collagen 4 alpha-5 (COL4A5)

^[1]^[2]^[3]^[4]^[5]^[6]

Function

type 4 collagen is the major structural component of glomerular basement membranes (GBM), forming a 'chicken-wire' meshwork together with laminins, proteoglycans and entactin/nidogen
Pro at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains
type 4 collagen contains numerous Cys which are involved in intermolecular & intramolecular disulfide bonding
- 12 of these, located in the NC1 domain, are conserved in all type 4 collagen
the trimeric structure of the NC1 domains is stabilized by covalent bonds between Lys & Met residues (putative)
there are six type 4 collagen isoforms, each of which can form a triple helix structure with 2 other chains to generate type 4 collagen network

alpha chains of type 4 collagen have
- a non-collagenous domain (NC1) at their C-terminus
- frequent interruptions of the G-X-Y repeats in the long central triple-helical domain (which may cause flexibility in the triple helix)
- short N-terminal triple-helical 7S domain
belongs to the type 4 collagen family
contains 1 collagen 4 NC1 (C-terminal non-collagenous) domain

isoform 2 is found in kidney

defects in COL4A5 are associated with hereditary nephritis, X-linked^[6]
defects in COL4A5 are the cause of Alport syndrome X-linked
deletions covering the N-terminal regions of COL4A5 & COL4A6, which are localized in a head-to-head manner, are found in the chromosome Xq22.3 centromeric deletion syndrome