collagen 9 alpha-1 (COL9A1)

Function

• structural component of hyaline cartilage & vitreous of the eye
• covalently linked to the telopeptides of type 2 collagen by Lys-derived cross-links
• Pro at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains heterotrimer of COL9A1, COL9A2 & COL9A3

Structure

• each subunit is composed of three triple-helical domains interspersed with non-collagenous domains
• the globular domain at the N-terminus of type 9 collagen represents the NC4 domain which may participate in electrostatic interactions with polyanionic glycosaminoglycans in cartilage
• belongs to the fibril-associated collagens with interrupted helices (FACIT) family
• contains 1 TSP N-terminal (TSPN) domain

Compartment

• secreted, extracellular space, extracellular matrix (putative)

Alternative splicing

• named isoforms=3
• additional isoforms seem to exist

Pathology

• defects in COL9A1 are the cause of:
  • multiple epiphyseal dysplasia type 6
  • Stickler syndrome type 4

More general terms

• collagen subunit
• glycoprotein

Component of

• collagen type-9 (FACIT collagen)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=1297
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:1297
• OMIM: https://mirror.omim.org/entry/120210
• OMIM: https://mirror.omim.org/entry/614134
• OMIM: https://mirror.omim.org/entry/614135
• UniProt: http://www.uniprot.org/uniprot/P20849.html