Abstract
Chlamydomonas reinhardtii has two matrix metalloproteases (MMP), Mmp1 and Mmp2. The Mmp1 is named gametolysin, which is responsible for lysis of gametic cell walls during mating, and the Mmp2 appears to function at the zygotic stage. In this study, we identified the third MMP, Mmp3 from the Chlamydomonas EST library and analyzed the structure and function at the nucleotide and protein levels.
The ORF of Mmp3 cDNA codes for 646 aa, shows 70 and 59% identity with Mmp1 and Mmp2, and contains the hallmark motif characteristic of metzinsin-type MMP. Northern blot analysis suggests that Mmp3 is expressed in vegetative cells, especially during G1 phase. Two antibodies raised against N-terminal and C-terminal regions of the mature Mmp3 recognized a common 65-kDa protein, which was detected significantly at the G1 phase of cell cycle. It is therefore possible that Mmp3 is related to lysis and/or loosening of cell wall for proliferation.
