DOMAIN-STRUCTURE AND CONFORMATION OF A CELLOBIOHYDROLASE FROM TRICHODERMA-PSEUDOKININGII S-38

A cellobiohydrolase (CBH) with a molecular mass of 66kD was purified f rom Trichoderma pseudokiningii S-38. Papain digestion produced a 59- t o 60-kD core domain with 54% of intact activity on crystalline cellulo se and with full activity against soluble substrates. Digestion produc ts also included two small peptides with molecular mass of about 3-4 k D, which are heavily glycosylated and difficult to purify; the mixed p eptides displayed the capacity to disorganize the cellulose fiber. The sequencing results indicated that the intact enzyme had a blocked N-t erminal and there was a 10-amino-acid sequence in the N-terminal of th e core protein of Ser-Gly-Thr-Ala-Val-Thr-Cys-Leu-Ala-Asp. Fluoresence and circular dichroism properties indicated that the core protein has an independent conformation and is conformationally similar to intact enzyme, suggesting that the spectroscopic properties of the intact en zyme come from the core protein.