4NOS: Inducible nitric oxide synthase

Human inducible nitric oxide synthase with inhibitor. Determined by X-ray diffraction at 2.25 Å resolution. Released 4 Feb 2000.

Method: X-ray diffraction
Resolution: 2.25 Å
Organism: Homo sapiens
Chains: 4
Atoms: 15,317
Mol. weight: 201.82 kDa
Ligands: H4B, ITU, H2B, HEM
Released: 4 Feb 2000

Explore 4NOS in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

4NOS contains 109 α-helices and 118 β-strands across 4 chains. Residue ranges use author residue numbering, as in the PDB file, from PDBe. To see them in 3D, choose the Cartoon representation with Secondary structure coloring: helices, sheets and coils get different colors.

Chain A: 26 helices, 31 β-strands

Element	Residues	Length	Sheet
β-strand	85-88	4	1
β-strand	89	1	2
β-strand	95-98	4	1
α-helix	100-103	4
β-strand	105	1	3
β-strand	111	1	4
β-strand	114	1	4
β-strand	115	1	5
α-helix	123-125	3
β-strand	126	1	6
α-helix	133-135	3
α-helix	136-152	17
α-helix	159-176	18
α-helix	183-195	13
α-helix	203-207	5
β-strand	210-213	4	7
α-helix	220-235	16
α-helix	236-238	3
β-strand	243-246	4	7
α-helix	248-250	3
β-strand	258-259	2	8
β-strand	263	1	7
β-strand	267	1	9
β-strand	269-271	3	10
β-strand	277-279	3	10
α-helix	281-283	3
α-helix	284-292	9
β-strand	304	1	9
α-helix	305-306	2
β-strand	307-310	4	8
α-helix	314-316	3
β-strand	317-319	3	8
α-helix	320-322	3
α-helix	323-325	3
β-strand	328-330	3	11
α-helix	337-342	6
β-strand	345-347	3	11
β-strand	351-352	2	7
β-strand	356-359	4	12
β-strand	362-364	3	12
β-strand	369-370	2	7
β-strand	373-374	2	13
α-helix	375-376	2
α-helix	377-382	6
α-helix	392-398	7
α-helix	406-408	3
α-helix	410-428	19
β-strand	433-434	2	13
α-helix	436-454	19
α-helix	461-464	4
α-helix	470-472	3
β-strand	478	1	2
β-strand	482	1	14
β-strand	484	1	3
β-strand	488-490	3	12
β-strand	491	1	6
α-helix	495-498	4

Chain B: 26 helices, 29 β-strands

Element	Residues	Length	Sheet
β-strand	85-88	4	15
β-strand	89	1	16
β-strand	95-98	4	15
α-helix	100-103	4
β-strand	111	1	17
β-strand	114	1	17
β-strand	115	1	14
β-strand	126	1	18
α-helix	133-135	3
α-helix	136-152	17
α-helix	159-176	18
α-helix	183-195	13
α-helix	203-205	3
β-strand	210-213	4	19
α-helix	220-235	16
α-helix	236-238	3
β-strand	243-246	4	19
α-helix	248-250	3
β-strand	258-259	2	20
β-strand	263	1	19
β-strand	267	1	21
β-strand	269-271	3	22
β-strand	277-279	3	22
α-helix	281-283	3
α-helix	284-292	9
α-helix	303	1
β-strand	304	1	21
α-helix	305-306	2
β-strand	307-310	4	20
α-helix	315-316	2
β-strand	317-319	3	20
α-helix	320-322	3
α-helix	323-325	3
β-strand	328-330	3	23
α-helix	337-342	6
β-strand	345-347	3	23
β-strand	351-352	2	19
β-strand	356-359	4	24
β-strand	362-364	3	24
β-strand	369-370	2	19
β-strand	373-374	2	25
α-helix	375-376	2
α-helix	377-382	6
α-helix	392-399	8
α-helix	406-408	3
α-helix	410-428	19
β-strand	433-434	2	25
α-helix	436-454	19
α-helix	461-464	4
α-helix	470-472	3
β-strand	478	1	16
β-strand	482	1	5
β-strand	488-490	3	24
β-strand	491	1	18
α-helix	495-498	4

Chain C: 29 helices, 31 β-strands

Element	Residues	Length	Sheet
β-strand	85-88	4	26
β-strand	89	1	27
β-strand	95-98	4	26
α-helix	100-103	4
β-strand	111	1	28
β-strand	114	1	28
β-strand	115	1	29
α-helix	123-125	3
β-strand	126	1	30
α-helix	133-135	3
α-helix	136-152	17
α-helix	159-176	18
α-helix	183-195	13
α-helix	203-205	3
β-strand	210-213	4	31
α-helix	220-235	16
α-helix	236-238	3
β-strand	243-246	4	31
α-helix	248-250	3
β-strand	258-259	2	32
β-strand	263	1	31
β-strand	267	1	33
β-strand	269-272	4	34
β-strand	276-279	4	34
α-helix	281-283	3
α-helix	284-292	9
α-helix	295-297	3
α-helix	303	1
β-strand	304	1	33
α-helix	305-306	2
β-strand	307-310	4	32
α-helix	314-316	3
β-strand	317-319	3	32
α-helix	323-325	3
β-strand	328-330	3	35
α-helix	337-342	6
β-strand	345-347	3	35
β-strand	351-352	2	31
β-strand	356-359	4	36
β-strand	362-364	3	36
β-strand	369-370	2	31
β-strand	374	1	37
α-helix	375-376	2
α-helix	377-382	6
α-helix	383-384	2
α-helix	392-399	8
α-helix	406-408	3
α-helix	410-428	19
β-strand	434	1	37
α-helix	436-454	19
β-strand	458	1	38
α-helix	461-464	4
α-helix	470-472	3
α-helix	474-477	4
β-strand	478	1	27
β-strand	481	1	38
β-strand	482	1	39
β-strand	488-490	3	36
β-strand	491	1	30
α-helix	495-497	3

Chain D: 28 helices, 27 β-strands

Element	Residues	Length	Sheet
β-strand	85-88	4	40
β-strand	89	1	41
β-strand	95-98	4	40
α-helix	100-103	4
β-strand	115	1	39
α-helix	123-125	3
β-strand	126	1	42
α-helix	133-135	3
α-helix	136-152	17
α-helix	159-176	18
α-helix	183-195	13
α-helix	203-205	3
β-strand	210-213	4	43
α-helix	220-235	16
α-helix	236-238	3
β-strand	243-246	4	43
α-helix	248-250	3
β-strand	258-259	2	44
β-strand	263	1	43
β-strand	267	1	45
β-strand	269-271	3	46
β-strand	277-279	3	46
α-helix	281-283	3
α-helix	284-292	9
β-strand	304	1	45
α-helix	305-306	2
β-strand	307-310	4	44
α-helix	314-316	3
β-strand	317-319	3	44
α-helix	320-322	3
α-helix	323-325	3
β-strand	328-330	3	47
α-helix	337-342	6
β-strand	345-347	3	47
β-strand	351-352	2	43
β-strand	356-359	4	48
β-strand	362-364	3	48
β-strand	369-370	2	43
β-strand	373-374	2	49
α-helix	375-376	2
α-helix	377-382	6
α-helix	383-384	2
α-helix	392-399	8
α-helix	406-408	3
α-helix	410-428	19
β-strand	433-434	2	49
α-helix	436-454	19
α-helix	461-464	4
α-helix	470-472	3
α-helix	474-477	4
β-strand	478	1	41
β-strand	482	1	29
β-strand	488-490	3	48
β-strand	491	1	42
α-helix	495-498	4

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Inducible nitric oxide synthase	A, B, C, D	protein	427	Homo sapiens	P35228 (AlphaFold model)

Sequence of entity 1 (A, B, C, D), FASTA

>4NOS_1 INDUCIBLE NITRIC OXIDE SYNTHASE (chains A, B, C, D)
PRHVRIKNWGSGMTFQDTLHHKAKGILTCRSKSCLGSIMTPKSLTRGPRDKPTPPDELLP
QAIEFVNQYYGSFKEAKIEEHLARVEAVTKEIETTGTYQLTGDELIFATKQAWRNAPRCI
GRIQWSNLQVFDARSCSTAREMFEHICRHVRYSTNNGNIRSAITVFPQRSDGKHDFRVWN
AQLIRYAGYQMPDGSIRGDPANVEFTQLCIDLGWKPKYGRFDVVPLVLQANGRDPELFEI
PPDLVLEVAMEHPKYEWFRELELKWYALPAVANMLLEVGGLEFPGCPFNGWYMGTEIGVR
DFCDVQRYNILEEVGRRMGLETHKLASLWKDQAVVEINIAVIHSFQKQNVTIMDHHSAAE
SFMKYMQNEYRSRGGCPADWIWLVPPMSGSITPVFHQEMLNYVLSPFYYYQVEAWKTHVW
QDEKRRP

Ligands and cofactors

ID	Name	Formula	Copies
H4B	5,6,7,8-tetrahydrobiopterin	C9 H15 N5 O3	3
ITU	Ethylisothiourea	C3 H8 N2 S	4
H2B	2-amino-6-(1,2-dihydroxy-propyl)-7,8-dihydro-6H-pteridin-4-one	C9 H13 N5 O3	1
HEM	Protoporphyrin IX containing FE	C34 H32 Fe N4 O4	4
ZN	Zinc ion	Zn	2

Primary citation

Structural characterization of nitric oxide synthase isoforms reveals striking active-site conservation. Fischmann, T.O., Hruza, A., Niu, X.D. et al. Nat Struct Biol (1999) 6:233-242. DOI 10.1038/6675 · PubMed

Other PDB entries of the same protein (UniProt P35228 (AlphaFold model), which also has an AlphaFold model), best resolution first:

6JWM 1.23 Å, Crystal structure of the SPRY domain of SPSB2 in complex with cR7, a potent cyclic…
6KEY 1.24 Å, Structural basis for the regulation of inducible nitric oxide synthase (iNOS) by the…
5XN3 1.34 Å, Crystal structure of SPSB2 in complex with a rational designed RGD containing cyclic…
6JWN 1.61 Å, Crystal structure of the SPRY domain of SPSB2 in complex with cR9, a cyclic peptide…
3E7G 2.2 Å, Structure of human INOSOX with inhibitor AR-C95791
3HR4 2.5 Å, Human iNOS Reductase and Calmodulin Complex
1NSI 2.55 Å, Human inducible nitric oxide synthase, ZN-bound, L-arg complex
3EJ8 2.55 Å, Structure of double mutant of human iNOS oxygenase domain with bound immidazole
2NSI 3.0 Å, Human inducible nitric oxide synthase, ZN-free, seitu complex
4CX7 3.16 Å, Structure of human iNOS heme domain in complex with (R)-6-(3-AMINO-2-(5-(2-(6-AMINO-4-…
2LL6 Solution NMR structure of CaM bound to iNOS CaM binding domain peptide
5TP6 Solution structure of the CaM34 with the iNOS CaM binding domain peptide

Browse structure collections

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