Sequence of egVand Properties of EgV, a Ruminococcus albusEndoglucanase Containing a Dockerin Domain

The Ruminococcus albusF-40 egVgene, encoding endoglucanase V (EGV), consists of an open reading frame of 1,833 nucleotides and encodes 611 amino acids with a deduced molecular weight of 67,103. The deduced EGV is a modular enzyme composed of a catalytic domain of family 5 of glycosyl hydrolases, a domain of unknown function, and a dockerin domain responsible for cellulosome assembly, suggesting that R. albusF-40 produces a cellulosome, and EGV is a component of the cellulosome. A truncated form of EGV with an apparent molecular weight of 42,000 was purified from a recounbinant Escherichia coliand characterized since EGV suffered from partial proteolysis by E. coliprotease(s). The truncated EGV was active toward carboxylmethyl cellulose, xylan, lichenan, and acid-swollen cellulose. The pH and temperature optima of the enzyme were 7.0 and 40°C, respectively. By Western blot analysis using the antiserum raised against the truncated enzylne, EGV was detected in the whole cells but not in the culture supernatant of R. alubusF-40, suggesting that EGV was located on the cell surface.