Type XIII Collagen and Some Other Transmembrane Collagens Contain Two Separate Coiled-coil Motifs, Which May Function as Independent Oligomerization Domains

Abstract

Type XIII collagen is a homotrimeric transmembrane collagen composed of a short intracellular domain, a single membrane-spanning region, and an extracellular ectodomain with three collagenous domains (COL1-3) separated by short non-collagenous domains (NC1-4). Several collagenous transmembrane proteins have been found to harbor a conserved sequence next to their membrane-spanning regions, and in the case of type XIII collagen this sequence has been demonstrated to be important for chain association. We show here that this 21-residue sequence is necessary but not sufficient for NC1 association. Furthermore, the NC1 association region was predicted to form an ␣-helical coiled-coil structure, which may already begin at the membrane-spanning region, as is also predicted for the related collagen types XXIII and XXV. Interestingly, a second coiled-coil structure is predicted to be located in the NC3 domain of type XIII collagen and in the corresponding domains of types XXIII and XXV. It is found experimentally that the absence of the NC1 coiled-coil domain leads to a lack of disulfide-bonded trimers and misfolding of the membrane-proximal collagenous domain COL1, whereas the COL2 and COL3 domains are correctly folded. We suggest that the NC1 coiled-coil domain is important for association of the N-terminal part of the type XIII collagen ␣ chains, whereas the NC3 coiled-coil domain is implicated in the association of the C-terminal part of the molecule. All in all, we propose that two widely separated coiled-coil domains of type XIII and related collagens function as independent oligomerization domains participating in the folding of distinct areas of the molecule.Type XIII collagen is a type II transmembrane protein that is expressed in many tissues throughout development and adult life (1). It is located in focal adhesions of cultured fibroblasts and other cells and in adhesive structures of tissues such as the myotendinous junctions in muscle, intercalated discs in heart, and the cell basement membrane interphases (1, 2). The type XIII collagen ectodomain can bind to fibronectin, heparin, the basement membrane components nidogen-2 and perlecan, and the ␣ 1 -subunit of integrin (3-5). Due to its location at the tissue and cell level and its binding properties, it has been postulated that type XIII collagen is involved in cellular adhesion and migration.Type XIII collagen ␣ chains produced in a recombinant insect cell culture system have been shown to form homotrimers (6). The primary structure is composed of three collagenous domains (COL1 1 to COL3), which are flanked and interrupted by non-collagenous domains (NC1 to NC4). The short cytosolic domain and the transmembrane domain encompass about half of the NC1 domain, whereas the rest of the molecule forms the ectodomain, which is a rod of about 150 nm with two flexible hinges coinciding with the NC2 and NC3 domains (5). The primary structures of COL1, NC2, COL3, and NC4 can vary, on account of complex alternative splicing (7-10). It has been shown recently that ext...

Noncollagenous region of the streptococcal collagen‐like protein is a trimerization domain that supports refolding of adjacent homologous and heterologous collagenous domains

“…The structures of many of these folding domains have been shown to contain three-stranded a-helical coiled-coil motifs, such as those in collectins and transmembrane collagens, and analysis shows that they can be located C-terminal as well as N-terminal to the triple-helix domain. [29][30][31] Meanwhile, high resolution structures have shown beta-sheet structures in the NC1 domains of network-forming collagens Type IV, Type VIII, and Type X, [32][33][34][35] and the C-terminal noncollagenous region of Type XVIII collagen. 36 Examination of bacterial collagens extends the categories of collagen folding domains.…”

A conserved trimerization motif controls the topology of short coiled coils

“…7, which is published as supporting information on the PNAS web site, potential interhelical g Arg to eЈ Glu salt bridges are found in many other short (15-50 aa in length) parallel trimeric coiled-coil domains of intracellular, extracellular, transmembrane, viral, and synthetic proteins. Several members of these autonomous coiled coils are well characterized (9,30,31,(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43). Based on the alignment, the sequence motif R 1 -h 2 -x 3 -x 4 -h 5 -E 6 can be deduced (R ϭ Arg; E ϭ Glu, L ϭ Leu; h 1 ϭ Ile, Leu, Val, Met; h 2 ϭ Leu, Ile, Val; x ϭ any amino acid residue).…”

Collagenous Transmembrane Proteins: Recent Insights into Biology and Pathology*

“…These linker regions contain trimeric ␣-helical coiled-coils thought to prompt trimerization and subsequent zipper-like folding of the adjacent triple helices, presumably in the N-to C-terminal direction (11)(12)(13)(14)(15).…”