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Joined 2026-09-21 Message
Incoming links: Collagen IV protomer
Collagen IV NC1 domain 2026-11-05
The Collagen IV NC1 domain is the noncollagenous protein domain at the C-terminus of a Collagen IV chain. NC1 regions participate in the end-to-end assembly of the network that supports a basement membrane. A three-chain Collagen IV protomer presents three NC1 regions at this end; association of two such ends forms a six-subunit Collagen IV NC1 hexamer.[ref]
A Sulfilimine Bond Identified in Collagen IV by Roberto Vanacore and others. Introduction and Figure 3; trimeric NC1 ends of adjoining protomers and hexamer organization
The counting is useful: a six-subunit junction joins two three-chain molecular units, rather than requiring each Collagen IV molecule to contain six chains. The Collagen IV NC1 hexamer describes a local meeting point in the larger scaffold.
The junction is reinforced by sulfilimine bonds between methionine and hydroxylysine residues of adjoining units. In 2009, mass spectrometry and nuclear magnetic resonance measurements on isolated linked peptides identified this bond. Chemical reduction separated the linked peptides, providing another test of the proposed structure. Up to six such links can reinforce the interface between the two NC1 ends.[ref]
Collagen IV NC1 hexamer 2026-11-05
A Collagen IV NC1 hexamer is a six-subunit junction formed when the C-terminus ends of two Collagen IV protomers associate. Each three-chain protomer contributes three Collagen IV NC1 domains. The resulting arrangement is therefore two three-subunit ends joined together, one local connection in a basement membrane scaffold.[ref]
A Sulfilimine Bond Identified in Collagen IV by Roberto Vanacore and others. Introduction and Figure 3; trimeric ends and six-subunit junction
Up to six sulfilimine bonds can reinforce the interface between the two ends. Analysis of linked peptides by mass spectrometry and nuclear magnetic resonance, followed by chemical reduction that separated the linked components, established the chemistry of this reinforcement.[ref]
A Sulfilimine Bond Identified in Collagen IV by Roberto Vanacore and others. Table 1 and Figures 1–3; crosslinked peptides, bond identification and reduction
Collagen IV protomer 2026-11-05
A Collagen IV protomer is a three-chain molecular unit of Collagen IV that assembles with other units to form a basement membrane network. Much of its length has a collagen triple helix, while its C-terminus presents three Collagen IV NC1 domains. Association of two such ends forms a Collagen IV NC1 hexamer.[ref]
A Sulfilimine Bond Identified in Collagen IV by Roberto Vanacore and others. Introduction and Figure 3; triple-helical protomers and end-to-end network assembly
The organizational levels can be counted separately. Ten intact three-chain Collagen IV protomers contain thirty polypeptide chains, but this count does not describe how the ten units are connected. A six-subunit NC1 junction joins two protomers at one end; it does not convert either protomer into a six-chain molecule.
The term is therefore useful when moving between a protein's molecular composition and the architecture of the scaffold it builds. Identifying a three-chain unit answers a different question from identifying the contacts and covalent bonds between neighbouring units.