1SFI: Trypsin

High resolution structure of a potent, cyclic protease inhibitor from sunflower seeds. Determined by X-ray diffraction at 1.65 Å resolution. Released 9 Jul 1999.

Method: X-ray diffraction
Resolution: 1.65 Å
Organisms: Bos taurus, Helianthus annuus
Chains: 2
Atoms: 2,126
Mol. weight: 25.19 kDa
Ligands: CA
Released: 9 Jul 1999

Explore 1SFI in 3D Show helices and sheets RCSB PDB PDBe

Secondary structure: helices and β-sheets

1SFI contains 8 α-helices and 20 β-strands across 2 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: 7 helices, 18 β-strands

Element	Residues	Length	Sheet
β-strand	17	1	1
β-strand	20-21	2	2
β-strand	30-34	5	3
β-strand	40-48	9	3
β-strand	51-54	4	3
α-helix	56-58	3
β-strand	64-67	4	3
β-strand	81-90	10	3
β-strand	104-108	5	3
α-helix	111-114	4
β-strand	122	1	2
α-helix	123-124	2
β-strand	135-140	6	2
β-strand	156-162	7	2
α-helix	163-164	2
α-helix	165-171	7
β-strand	180-183	4	2
β-strand	189	1	1
β-strand	198-201	4	2
β-strand	204-217	10	2
β-strand	221	1	4
β-strand	224	1	4
β-strand	226-230	5	2
α-helix	231-234	4
α-helix	235-244	10

Chain I: 1 helix, 2 β-strands

Element	Residues	Length	Sheet
β-strand	2-4	3	2
α-helix	9-10	2
β-strand	11	1	2

Molecules and chains

Molecule	Chains	Type	Length	Organism	UniProt
Trypsin	A	protein	223	Bos taurus	P00760 (AlphaFold model)
Trypsin inhibitor 1	I	protein	14	Helianthus annuus	Q4GWU5 (AlphaFold model)

Sequence of entity 1 (A), FASTA

>1SFI_1 TRYPSIN (chains A)
IVGGYTCGANTVPYQVSLNSGYHFCGGSLINSQWVVSAAHCYKSGIQVRLGEDNINVVEG
NEQFISASKSIVHPSYNSNTLNNDIMLIKLKSAASLNSRVASISLPTSCASAGTQCLISG
WGNTKSSGTSYPDVLKCLKAPILSDSSCKSAYPGQITSNMFCAGYLEGGKDSCQGDSGGP
VVCSGKLQGIVSWGSGCAQKNKPGVYTKVCNYVSWIKQTIASN

Sequence of entity 2 (I), FASTA

>1SFI_2 Trypsin inhibitor 1 (chains I)
GRCTKSIPPICFPD

Ligands and cofactors

ID	Name	Formula	Copies
CA	Calcium ion	Ca	1

Water and common crystallization additives (SO4) are not listed.

Primary citation

High-resolution structure of a potent, cyclic proteinase inhibitor from sunflower seeds. Luckett, S., Garcia, R.S., Barker, J.J. et al. J Mol Biol (1999) 290:525-533. DOI 10.1006/jmbi.1999.2891 · PubMed

Other PDB entries of the same protein (UniProt P00760 (AlphaFold model), which also has an AlphaFold model), best resolution first:

4I8H 0.75 Å, Bovine trypsin at 0.75 resolution
5MN1 0.79 Å, Cationic trypsin in complex with 2-aminopyridine (deuterated sample at 100 K)
5MNK 0.8 Å, Cationic trypsin in complex with benzylamine (deuterated sample at 100 K)
3MFJ 0.8 Å, Bovine trypsin at 0.8 A resolution, restrained refinement
3MI4 0.8 Å, Bovine trypsin at 0.8 A resolution, non-restrained refinement
4I8G 0.8 Å, Bovine trypsin at 0.8 resolution
4I8K 0.85 Å, Bovine trypsin at 0.85 resolution
5MNN 0.86 Å, Cationic trypsin in complex with N-amidinopiperidine (deuterated sample at 100 K)
5MNG 0.86 Å, Cationic trypsin in complex with benzamidine (deuterated sample at 100 K)
4I8J 0.87 Å, Bovine trypsin at 0.87 A resolution
4I8L 0.87 Å, Bovine trypsin at 0.87 resolution
4XOJ 0.91 Å, Structure of bovine trypsin in complex with analogues of sunflower inhibitor 1 (SFTI-1)

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