Biotin Protein Ligase from Saccharomyces cerevisiae

revealed that the sequence between resi-dues 240 and 260 was extremely sensitive to proteolysis,suggesting that it forms an exposed linker between anN-terminal 27-kDa domain and the C-terminal 50-kDadomain containing the active site. The protease suscep-tibility of this linker region was considerably reduced inthe presence of ATP and biotin. A second protease-sen-sitive sequence, located in the presumptive catalyticsite, was protected against digestion by the substrates.Expression of N-terminally truncated variants of theyeast enzyme failed to complement