SUPERFAMILY 1.75 HMM library and genome assignments server

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Subtilisin inhibitor superfamily

SCOP classification
Root:   SCOP hierarchy in SUPERFAMILY [ 0] (11)
Class:   Alpha and beta proteins (a+b) [ 53931] (376)
Fold:   Subtilisin inhibitor [ 55398]
Superfamily:   Subtilisin inhibitor [ 55399]
Families:   Subtilisin inhibitor [ 55400]

Superfamily statistics
Genomes (52) Uniprot 2018_03 genome PDB chains (SCOP 1.75)
Domains 98 1,581 5
Proteins 98 1,580 5

Functional annotation
General category Processes_IC
Detailed category Proteases

Function annotation of SCOP domain superfamilies

InterPro annotation
Cross references IPR000691 SSF55399 Protein matches

The Streptomyces family of bacteria produce a number of proteinase inhibitors, which belong to MEROPS inhibitor family I16, clan IY. They are characterised by their strong activity towards subtilisin (MEROPS peptidase family S8, ) and are collectively known as Streptomyces subtilisin inhibitors (SSI). Some SSI also inhibit trypsin, chymotrypsin (MEROPS peptidase family S1, ) and griselysin (MEROPS peptidase family M4, ) [PubMed14705960]. Mutation of the active site residue can influence inhibition specificity [PubMed1908859]. SSI is a homodimer, each monomer containing 2 anti-parallel beta-sheets and 2 short alpha-helices. Protease binding induces the widening of a channel-like structure, in which hydrophobic side-chains are sandwiched between 2 lobes [PubMed6387152]. Loss of the C-terminal tetrapeptide VFAF drastically reduces the inhibitory effect of the proteins when there is less than one molecule of inhibitor present per molecule of enzyme. This implies that the tetrapeptide is neccessary to maintain the correct 3D fold [PubMed6993452]. Structural similarities between the primary and secondary contact loops of SSI, and the ovomucoid and pancreatic secretory trypsin inhibitor family suggest evolution of the 2 families from a common ancestor [PubMed6387152].

InterPro database

PDBeMotif information about ligands, sequence and structure motifs
Cross references PDB entries
Ligand binding statistics
Nucleic-acid binding statistics
Occurrence of secondary structure elements
Occurrence of small 3D structural motifs

PDBeMotif resource

Jump to [ Top of page · SCOP classification · InterPro annotation · PDBeMotif links · Functional annotation ]

Internal database links

Browse genome assignments for this superfamily. The SUPERFAMILY hidden Markov model library has been used to carry out SCOP domain assignments to all genomes at the superfamily level.

Alignments of sequences to 2 models in this superfamily are available by clicking on the 'Alignments' icon above. PDB sequences less than 40% identical are shown by default, but any other sequence(s) may be aligned. Select PDB sequences, genome sequences, or paste in or upload your own sequences.

Browse and view proteins in genomes which have different domain combinations including a Subtilisin inhibitor domain.

Examine the distribution of domain superfamilies, or families, across the major taxonomic kingdoms or genomes within a kingdom. This gives an immediate impression of how superfamilies, or families, are restricted to certain kingdoms of life.

Explore domain occurrence network where nodes represent genomes and edges are domain architectures (shared between genomes) containing the superfamily of interest.

There are 2 hidden Markov models representing the Subtilisin inhibitor superfamily. Information on how the models are built, and plots showing hydrophobicity, match emmission probabilities and insertion/deletion probabilities can be inspected.

Jump to [ Top of page · SCOP classification · InterPro annotation · PDBeMotif links · Functional annotation · Internal database links ]