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From Proteopedia
ASSEMBLY DOMAIN OF CARTILAGE OLIGOMERIC MATRIX PROTEIN IN COMPLEX WITH ALL-TRANS RETINOL
Structural highlights
FunctionCOMP_RAT May play a role in the structural integrity of cartilage via its interaction with other extracellular matrix proteins such as the collagens and fibronectin. Can mediate the interaction of chondrocytes with the cartilage extracellular matrix through interaction with cell surface integrin receptors. Could play a role in the pathogenesis of osteoarthritis. Potent suppressor of apoptosis in both primary chondrocytes and transformed cells. Suppresses apoptosis by blocking the activation of caspase-3 and by inducing the IAP family of survival proteins (BIRC3, BIRC2, BIRC5 and XIAP) (By similarity). Essential for maintaining a vascular smooth muscle cells (VSMCs) contractile/differentiated phenotype under physiological and pathological stimuli. Maintains this phenotype of VSMCs by interacting with ITGA7. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe potential storage and delivery function of cartilage oligomeric matrix protein (COMP) for cell signaling molecules was explored by binding hydrophobic compounds to the recombinant five-stranded coiled-coil domain of COMP. Complex formation with benzene, cyclohexane, vitamin D3 and elaidic acid was demonstrated through increases in denaturation temperatures of 2-10 degreesC. For all-trans retinol and all-trans retinoic acid, an equilibrium dissociation constant KD = 0.6 microM was evaluated by fluorescence titration. Binding of benzene and all-trans retinol into the hydrophobic axial pore of the COMP coiled-coil domain was proven by the X-ray crystal structures of the corresponding complexes at 0.25 and 0.27 nm resolution, respectively. Benzene binds with its plane perpendicular to the pore axis. The binding site is between the two internal rings formed by Leu37 and Thr40 pointing into the pore of the COMP coiled-coil domain. The retinol beta-ionone ring is positioned in a hydrophobic environment near Thr40, and the 1.1 nm long isoprene tail follows a completely hydrophobic region of the pore. Its terminal hydroxyl group complexes with a ring of the five side chains of Gln54. A mutant in which Gln54 is replaced by Ile binds all-trans retinol with affinity similar to the wild-type, demonstrating that hydrophobic interactions are predominant. All-trans retinol, vitamin D and other hydrophobic compounds bind in the axial pore of the five-stranded coiled-coil domain of cartilage oligomeric matrix protein.,Guo Y, Bozic D, Malashkevich VN, Kammerer RA, Schulthess T, Engel J EMBO J. 1998 Sep 15;17(18):5265-72. PMID:9736606[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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