THE STRUCTURE OF BACILLUS-SUBTILIS PECTATE LYASE IN COMPLEX WITH CALCIUM

We have solved the structure of the Bacillus subtilis pectate lyase (B sPel) in complex with calcium, The structure consists of a parallel be ta-helix domain and a loop region. The alpha(L)-bounded beta-strand se en in BsPel is a new element of protein structure and its frequent occ urrence suggests it is an important characteristic of the parallel bet a-helix, A pronounced cleft is formed between the loops and the parall el beta-helix domain and we propose that this is the active site deft. Calcium, essential for the activity of the enzyme, binds at the botto m of this cleft and an arginine residue dose to the calcium, which is conserved across all pectin and pectate lyases, may be involved in cat alysis.