Collagens transmembrane

Transmembrane Collagens (Types XIII, XVII, XXIII, and XXV) 491... 

Transmembrane collagen Basement membrane Basement membrane zone FACIT-like XVI, XIX... 

Most types of collagen are extracellular matrix proteins but four of the vertebrate collagens (XIII, XVII, XXIII, and XXV) are classified as type II membrane proteins. They contain an N-terminal cytoplasmic domain, a transmembrane domain, and an extracellular collagenous domain. Also, a membrane-bound protein, ectodys-plasin-A, is a membrane protein with 19 -Gly-Xaa-Yaa- repeat. Macrophage scavenger receptor, ... 

Type XXIII collagen contains about 540 residues. The NCI domain contains a transmembrane sequence and is followed by COLl, NC2, COL2, NC3, COL3, and NC4 at the C-terminus. Furin proteinases may cleave the NCI domain, and the cleaved secreted portion of type XXIII collagen may also form multimers and display low-affinity binding to heparin in vitro ... 

The mineralized matrix of bone tissue is strained when loaded. Macro-molecular mechanical connections between the extracellular matrix and the osteocytic cell membrane exist and these connections may be capable of transmitting information from the strained extracellular matrix to the bone cell nuclear membrane. The basis of this mechanism is the physical continuity of the transmembrane integrin molecule, which is connected extracellularly with the macromolecular collagen of the organic matrix and intracellularly with the... 

Procollagen proline 4-hydroxylase is the best studied of this class of enzymes it is assumed that the others have essentially the same mechanism, although proline and lysine hydroxylases show very little sequence homology (Kivirikko and Pihlajaniemi, 1998). Although 3-hydroxyproline is found only in collagen, 4-hydroxyproline and hydroxylysine are found in a variety of other proteins, including the Clq component of complement, osteocalcin, macrophage receptor proteins, and a variety of transmembrane and intercellular proteins and proteins of the cytoskeleton, as weU as some enzymes. 4-Hydroxyproline, but not hydroxylysine, also occurs in elastin. 

Fig. 4.4 Integrins are transmembrane receptors. They are activated by components of the extracellular matnx, such as fibronectin and collagen. These interactions lead to clustering of integrin receptors and the formation of focal adhesions, intracellular cytoskeletal complexes, and formation of actin bundles.30 Activation of integrins is part of the celi-ceil adhesion process, integrins also bind to adhesion moiecules on adjacent celis.

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