Protein profile

PA0928

sensor/response regulator hybrid protein

Genome: NC_002516.2

Gene: gacS PA0928 Structure source: Experimental + AlphaFold UniProt G3XD98

Export view

Amino acids 925

Annotations 12

Features 73

PDB binders 4

Druggability 0.787

Overview

Basic information about this protein and its source genome.

Accession: PA0928
Assembly: Pseudomonas aeruginosa PAO1, complete genome
Gene: gacS PA0928
Status: annotated
Amino acids: 925
Structure source: Experimental + AlphaFold

2.7.13.3

GO:0005886 The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins. GO:0005524 Binding to ATP, adenosine 5'-triphosphate, a universally important coenzyme and enzyme regulator. GO:0046872 Binding to a metal ion. GO:0000155 Catalysis of the phosphorylation of a histidine residue in response to detection of an extracellular signal such as a chemical ligand or change in environment, to initiate a change in cell state or activity. The two-component sensor is a histidine kinase that autophosphorylates a histidine residue in its active site. The phosphate is then transferred to an aspartate residue in a downstream response regulator, to trigger a response. GO:2000147 Any process that activates or increases the frequency, rate or extent of cell motility. GO:1900378 Any process that activates or increases the frequency, rate or extent of secondary metabolite biosynthetic process.

Target profile

Computed evidence for target prioritization.

Human off-target: No hit
Gut microbiome off-target: hit
Essential (DEG): N
Localization: CytoplasmicMembrane

Selected Druggability evidence

Selected Druggability is the FPocket score chosen for ranking using the curated structure priority. The 3D viewer may show a different loaded structure, so its visible pockets can differ.

FPocket 0.787

Structure –

Pocket –

Sequence

Primary amino-acid sequence viewer.

Functional Annotations

Enzyme classification and Gene Ontology terms linked to this protein.

1 EC 11 GO

Enzyme Commission (EC)

2.7.13.3

Gene Ontology (GO)

GO:0005886 The membrane surrounding a cell that separates the cell from its external environment. It consists of a phospholipid bilayer and associated proteins.
GO:0005524 Binding to ATP, adenosine 5'-triphosphate, a universally important coenzyme and enzyme regulator.
GO:0046872 Binding to a metal ion.
GO:0000155 Catalysis of the phosphorylation of a histidine residue in response to detection of an extracellular signal such as a chemical ligand or change in environment, to initiate a change in cell state or activity. The two-component sensor is a histidine kinase that autophosphorylates a histidine residue in its active site. The phosphate is then transferred to an aspartate residue in a downstream response regulator, to trigger a response.
GO:2000147 Any process that activates or increases the frequency, rate or extent of cell motility.
GO:1900378 Any process that activates or increases the frequency, rate or extent of secondary metabolite biosynthetic process.
GO:0016020 A lipid bilayer along with all the proteins and protein complexes embedded in it and attached to it.
GO:0000160 A conserved series of molecular signals found in prokaryotes and eukaryotes; involves autophosphorylation of a histidine kinase and the transfer of the phosphate group to an aspartate that then acts as a phospho-donor to response regulator proteins.
GO:0007165 The cellular process in which a signal is conveyed to trigger a change in the activity or state of a cell. Signal transduction begins with reception of a signal (e.g. a ligand binding to a receptor or receptor activation by a stimulus such as light), or for signal transduction in the absence of ligand, signal-withdrawal or the activity of a constitutively active receptor. Signal transduction ends with regulation of a downstream cellular process, e.g. regulation of transcription or regulation of a metabolic process. Signal transduction covers signaling from receptors located on the surface of the cell and signaling via molecules located within the cell. For signaling between cells, signal transduction is restricted to events at and within the receiving cell.
GO:0016772 Catalysis of the transfer of a phosphorus-containing group from one compound (donor) to another (acceptor).
GO:0016310 The process of introducing a phosphate group into a molecule, usually with the formation of a phosphoric ester, a phosphoric anhydride or a phosphoric amide.

Sequence Features

Domain/signature hits from InterPro and related databases.

73 records

Show feature table

Start	End	DB	Term	Name
281	344	CDD	cd00082	HisKA
281	344	InterPro	IPR003661	Signal transduction histidine kinase, dimerisation/phosphoacceptor domain
337	509	SUPERFAMILY	SSF55874	ATPase domain of HSP90 chaperone/DNA topoisomerase II/histidine kinase
337	509	InterPro	IPR036890	Histidine kinase/HSP90-like ATPase superfamily
395	510	Pfam	PF02518	Histidine kinase-, DNA gyrase B-, and HSP90-like ATPase
395	510	InterPro	IPR003594	Histidine kinase/HSP90-like ATPase
227	787	PANTHER	PTHR45339	HYBRID SIGNAL TRANSDUCTION HISTIDINE KINASE J
28	167	Phobius	NON_CYTOPLASMIC_DOMAIN	Region of a membrane-bound protein predicted to be outside the membrane, in the extracellular region.
249	346	Gene3D	G3DSA:1.10.287.130	-
290	511	ProSiteProfiles	PS50109	Histidine kinase domain profile.
290	511	InterPro	IPR005467	Histidine kinase domain
395	511	SMART	SM00387	HKATPase_4
395	511	InterPro	IPR003594	Histidine kinase/HSP90-like ATPase
657	786	Gene3D	G3DSA:3.40.50.2300	-
168	187	TMHMM	TMhelix	Region of a membrane-bound protein predicted to be embedded in the membrane.
764	901	SUPERFAMILY	SSF47226	Histidine-containing phosphotransfer domain, HPT domain
764	901	InterPro	IPR036641	HPT domain superfamily
666	785	ProSiteProfiles	PS50110	Response regulatory domain profile.
666	785	InterPro	IPR001789	Signal transduction response regulator, receiver domain
665	781	SMART	SM00448	REC_2
665	781	InterPro	IPR001789	Signal transduction response regulator, receiver domain
11	22	Phobius	SIGNAL_PEPTIDE_H_REGION	Hydrophobic region of a signal peptide.
436	450	PRINTS	PR00344	Bacterial sensor protein C-terminal signature
436	450	InterPro	IPR004358	Signal transduction histidine kinase-related protein, C-terminal
471	489	PRINTS	PR00344	Bacterial sensor protein C-terminal signature
471	489	InterPro	IPR004358	Signal transduction histidine kinase-related protein, C-terminal
454	464	PRINTS	PR00344	Bacterial sensor protein C-terminal signature
454	464	InterPro	IPR004358	Signal transduction histidine kinase-related protein, C-terminal
495	508	PRINTS	PR00344	Bacterial sensor protein C-terminal signature
495	508	InterPro	IPR004358	Signal transduction histidine kinase-related protein, C-terminal
191	243	ProSiteProfiles	PS50885	HAMP domain profile.
191	243	InterPro	IPR003660	HAMP domain
284	348	Pfam	PF00512	His Kinase A (phospho-acceptor) domain
284	348	InterPro	IPR003661	Signal transduction histidine kinase, dimerisation/phosphoacceptor domain
839	906	CDD	cd00088	HPT
839	906	InterPro	IPR008207	Signal transduction histidine kinase, phosphotransfer (Hpt) domain
347	513	FunFam	G3DSA:3.30.565.10:FF:000010	Sensor histidine kinase RcsC
168	187	Phobius	TRANSMEMBRANE	Region of a membrane-bound protein predicted to be embedded in the membrane.
820	912	ProSiteProfiles	PS50894	Histidine-containing phosphotransfer (HPt) domain profile.
820	912	InterPro	IPR008207	Signal transduction histidine kinase, phosphotransfer (Hpt) domain
191	243	SMART	SM00304	HAMP_11
36	167	Pfam	PF09984	Single cache domain 4
36	167	InterPro	IPR019247	Histidine kinase BarA, N-terminal
196	238	CDD	cd06225	HAMP
1	27	Phobius	SIGNAL_PEPTIDE	Signal peptide region
817	913	SMART	SM00073	hpt_2
817	913	InterPro	IPR008207	Signal transduction histidine kinase, phosphotransfer (Hpt) domain
248	346	FunFam	G3DSA:1.10.287.130:FF:000003	Histidine kinase
191	240	SUPERFAMILY	SSF158472	HAMP domain-like
400	509	CDD	cd16922	HATPase_EvgS-ArcB-TorS-like
11	33	TMHMM	TMhelix	Region of a membrane-bound protein predicted to be embedded in the membrane.
1	10	Phobius	SIGNAL_PEPTIDE_N_REGION	N-terminal region of a signal peptide.
188	925	Phobius	CYTOPLASMIC_DOMAIN	Region of a membrane-bound protein predicted to be outside the membrane, in the cytoplasm.
667	781	CDD	cd17546	REC_hyHK_CKI1_RcsC-like
668	781	Pfam	PF00072	Response regulator receiver domain
668	781	InterPro	IPR001789	Signal transduction response regulator, receiver domain
663	786	SUPERFAMILY	SSF52172	CheY-like
663	786	InterPro	IPR011006	CheY-like superfamily
804	918	Gene3D	G3DSA:1.20.120.160	HPT domain
804	918	InterPro	IPR036641	HPT domain superfamily
283	348	SMART	SM00388	HisKA_10
283	348	InterPro	IPR003661	Signal transduction histidine kinase, dimerisation/phosphoacceptor domain
826	907	Pfam	PF01627	Hpt domain
826	907	InterPro	IPR008207	Signal transduction histidine kinase, phosphotransfer (Hpt) domain
162	248	Gene3D	G3DSA:6.10.340.10	-
347	515	Gene3D	G3DSA:3.30.565.10	-
347	515	InterPro	IPR036890	Histidine kinase/HSP90-like ATPase superfamily
224	255	Coils	Coil	Coil
189	239	Pfam	PF00672	HAMP domain
189	239	InterPro	IPR003660	HAMP domain
23	27	Phobius	SIGNAL_PEPTIDE_C_REGION	C-terminal region of a signal peptide.
269	349	SUPERFAMILY	SSF47384	Homodimeric domain of signal transducing histidine kinase
269	349	InterPro	IPR036097	Signal transduction histidine kinase, dimerisation/phosphoacceptor domain superfamily

3D Structure

Selected loaded structure. Experimental PDB entries may cover only a portion of the sequence; predicted models typically cover the full protein.

Loading 3D structure...

Legend High Medium Low

Structural evidence

4 + 1

Experimental PDB entries and predicted models. Click Switch to display a different structure in the viewer.

Entry	Method	Resolution	Chain	Coverage	Links	Status
PDB 7Z8N	X-ray	2.64 Å	A,B,C,D	31.7% 220-512	PDBe RCSB PDBj File	Viewing
PDB 7QZO	X-ray	1.45 Å	A,B	14.3% 662-793	PDBe RCSB PDBj File	Loaded
PDB 7QZ2	X-ray	1.87 Å	A,B	14.3% 662-793	PDBe RCSB PDBj File	Loaded
PDB 7N0E	X-ray	2.30 Å	A	6.5% 285-344	PDBe RCSB PDBj File	Loaded
AlphaFold PA0928	AlphaFold	—	—	full sequence	—	Loaded

Pocket details FPocket · P2Rank — toggle visibility and zoom from here, or open full viewer

Pockets (FPOCKET)

Showing top-ranked FPocket candidates by druggability. Druggability is color-coded: high (0.7 or higher), medium (0.4 to 0.69), low (below 0.4).

FPOCKET	Sticks	Spheres	Surfaces	Druggability	Labels	Zoom	Positions
1				0.755
4				0.364
22				0.233
3				0.202

Ligand evidence

Ligands grouped by evidence source. PDB ligands keep the source crystal visible, and loaded crystals can be opened directly in the structure viewer.

54 records

Highest-confidence structural evidence: ligands co-crystallized with this exact protein. If the source PDB is loaded in TPW, use Open crystal to inspect it in the structure viewer.

No PDB structure with a co-crystallized ligand found for this exact protein.

Structural evidence inferred from similar proteins. The source crystal indicates where the ligand was observed; the UniProt column identifies the homologous protein carrying that ligand.

Ligand	Source crystal	UniProt (homolog)	MW · LogP · TPSA	Lipinski	PAINS	SMILES
ANP	6QRJ	Q9ABT2	506.2 Da LogP -2.06 TPSA 281.9	3 viol.	✓ Clean	`c1nc(c2c(n1)n(cn2)[C@H]3[C@@H]([C@@H]([C@H](O3)…`
BEF	5N2N	O22267	66.0 Da LogP 0.88 TPSA 0.0	✓ Ro5	✓ Clean	`[Be-](F)(F)F`
BTB	3IQT	P0AEC6	209.2 Da LogP -3.01 TPSA 104.4	✓ Ro5	✓ Clean	`C(CO)N(CCO)C(CO)(CO)CO`
PG0	5UKV	P71815	120.1 Da LogP -0.36 TPSA 38.7	✓ Ro5	✓ Clean	`COCCOCCO`

Experimental bioactivity from ChEMBL measured directly on this protein. Score = pchembl (−log Ki/IC₅₀; higher = more potent).

No ChEMBL bioactivity data found for this exact protein.

Bioactivity inferred from similar proteins in ChEMBL. Score = pchembl (−log Ki/IC₅₀; higher = more potent).

No ChEMBL hits found through similar proteins.

Proposed virtual-screening candidates from ZINC. Score = Tanimoto similarity to a known binder (0–1; higher = more similar).

Ligand	Tanimoto	MW · LogP · TPSA	Lipinski	PAINS	SMILES
ZINC1580161	1.000	208.3 Da LogP -0.33 TPSA 57.2	✓ Ro5	✓ Clean	`COCCOCCOCCOCCO`
ZINC16052118	1.000	340.4 Da LogP -0.28 TPSA 84.8	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCOCCOCCO`
ZINC16052257	1.000	384.5 Da LogP -0.26 TPSA 94.1	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCOCCOCCOCCO`
ZINC1615342	1.000	209.2 Da LogP -3.01 TPSA 104.4	✓ Ro5	✓ Clean	`OCCN(CCO)C(CO)(CO)CO`
ZINC34317654	1.000	472.6 Da LogP -0.23 TPSA 112.5	1 viol.	✓ Clean	`COCCOCCOCCOCCOCCOCCOCCOCCOCCOCCO`
ZINC44076059	1.000	428.5 Da LogP -0.24 TPSA 103.3	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCOCCOCCOCCOCCO`
ZINC5210101	1.000	252.3 Da LogP -0.31 TPSA 66.4	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCO`
ZINC5997860	1.000	296.4 Da LogP -0.29 TPSA 75.6	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCOCCO`
ZINC12360002	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)OP(=O…`
ZINC12360703	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)OP(=O…`
ZINC12503599	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)OP(=O…`
ZINC16546165	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@H](CO[P@](=O)(O)OP(=O)(…`
ZINC31977053	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](CO[P@](=O)(O)OP(=O)…`
ZINC4806433	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)OP(=O…`
ZINC53683898	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](CO[P@@](=O)(O)OP(=…`
ZINC8586019	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](CO[P@](=O)(O)OP(=O)…`
ZINC8586020	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](CO[P@@](=O)(O)OP(=…`
ZINC8586021	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](CO[P@@](=O)(O)OP(=O…`
ZINC8586022	0.810	427.2 Da LogP -1.75 TPSA 232.6	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](CO[P@@](=O)(O)OP(=…`
ZINC13518964	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](COP(=O)(O)O)[C@H](…`
ZINC1532515	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](COP(=O)(O)O)[C@H](O…`
ZINC1571045	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](COP(=O)(O)O)[C@@H]…`
ZINC1842158	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](COP(=O)(O)O)[C@H](O…`
ZINC2046931	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](COP(=O)(O)O)[C@H](…`
ZINC2126310	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(=O)(O)O)[C@@H](…`
ZINC3201891	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](COP(=O)(O)O)[C@@H]…`
ZINC3201893	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](COP(=O)(O)O)[C@@H](…`
ZINC3830180	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@@H](COP(=O)(O)O)[C@@H](…`
ZINC3860156	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(=O)(O)O)[C@@H](…`
ZINC3977897	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@H](COP(=O)(O)O)[C@@H](O…`
ZINC4806442	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(=O)(O)O)[C@H](O…`
ZINC8613167	0.741	347.2 Da LogP -1.86 TPSA 186.1	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(=O)(O)O)[C@H](O…`
ZINC4096224	0.729	346.2 Da LogP -1.90 TPSA 191.9	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@](N)(=O)O)[C@@…`
ZINC575419714	0.727	312.4 Da LogP 0.42 TPSA 66.4	✓ Ro5	✓ Clean	`COCCOCCOCCSCCOCCOCCO`
ZINC12503850	0.726	427.3 Da LogP -2.04 TPSA 229.4	1 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@](=O)(O)OS(=O)…`
ZINC141161066	0.726	427.3 Da LogP -2.04 TPSA 229.4	1 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@](=O)(O)OS(=O)…`
ZINC141163786	0.726	427.3 Da LogP -2.04 TPSA 229.4	1 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@](=O)(O)OS(=O)…`
ZINC4228246	0.726	427.3 Da LogP -2.04 TPSA 229.4	1 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)OS(=O…`
ZINC105372833	0.712	345.3 Da LogP -1.93 TPSA 197.6	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(N)(N)=O)[C@H](O…`
ZINC105372837	0.712	345.3 Da LogP -1.93 TPSA 197.6	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(N)(N)=O)[C@H](O…`
ZINC17107643	0.712	345.3 Da LogP -1.93 TPSA 197.6	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(N)(N)=O)[C@@H](…`
ZINC204538551	0.712	345.3 Da LogP -1.93 TPSA 197.6	✓ Ro5	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](COP(N)(N)=O)[C@@H](…`
ZINC31475423	0.703	434.3 Da LogP -2.99 TPSA 238.4	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@H]1O[C@H](CO[P@@](=O)(O)OC(=O)…`
ZINC115163232	0.700	222.3 Da LogP 0.07 TPSA 57.2	✓ Ro5	✓ Clean	`COCCOCCOCCOCCCO`
ZINC1532902	0.700	206.2 Da LogP -0.86 TPSA 132.1	✓ Ro5	✓ Clean	`O=C(O)CC[C@@](O)(CC(=O)O)C(=O)O`
ZINC2018106	0.700	206.2 Da LogP -0.86 TPSA 132.1	✓ Ro5	✓ Clean	`O=C(O)CC[C@](O)(CC(=O)O)C(=O)O`
ZINC258837490	0.700	354.4 Da LogP 0.11 TPSA 84.8	✓ Ro5	✓ Clean	`COCCOCCOCCOCCOCCOCCOCCCO`
ZINC105469665	0.694	425.2 Da LogP -1.64 TPSA 223.4	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@@](=O)(O)CP(=O…`
ZINC219330894	0.694	425.2 Da LogP -1.64 TPSA 223.4	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@H](CO[P@](=O)(O)CP(=O)…`
ZINC3873855	0.694	425.2 Da LogP -1.64 TPSA 223.4	2 viol.	✓ Clean	`Nc1ncnc2c1ncn2[C@@H]1O[C@@H](CO[P@](=O)(O)CP(=O…`

PDB and ChEMBL records on this protein are shown in full. ChEMBL records from similar proteins are capped at the top 100 per protein (by pchembl) and ZINC at the top 50 (Tanimoto ≥ 0.5). ADME columns are descriptor-based screening flags, not experimental toxicity results.