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General Comment |
A cDNA encoding a new human matrix metalloproteinase (MMP), tentatively called MMP-23, has been cloned from an
ovary cDNA library by Velasco et al . This protein exhibits sequence similarity with MMPs, but displays a different domain structure. Thus,
MMP-23 lacks a recognizable signal sequence and has a short prodomain, although it contains a single cysteine residue that
can be part of the cysteine-switch mechanism operating for maintaining enzyme latency. The C-terminal domain is
considerably shortened and shows no sequence similarity to hemopexin, whereas all human MMPs, with the exception of
matrilysin, contain four hemopexin-like repeats. Furthermore, MMP-23 is devoid of structural features distinctive of the
diverse MMP subclasses, including the specific residues located close to the zinc-binding site in collagenases, the
transmembrane domain of membrane-type MMPs, or the fibronectin-like domain of gelatinases. Recombinant MMP-23 produced in Escherichia coli exhibits low, but significant proteolytic activity against
a synthetic substrate commonly used for assaying MMPs. Northern blot analysis demonstrated that MMP-23 is predominantly
expressed in ovary, testis, and prostate, suggesting that this new MMP may play a specialized role in reproductive processes.
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