SOLUTION STRUCTURE OF PORCINE PANCREATIC PROCOLIPASE AS DETERMINED FROM H-1 HOMONUCLEAR 2-DIMENSIONAL AND 3-DIMENSIONAL NMR

Procolipase is the precursor of colipase, which acts as protein cofact or for the activity of pancreatic lipase. The solution structure of pr ocolipase has been determined by H-1 NMR using two- and three-dimensio nal measurements. The secondary structure determination identified two separate three-stranded beta-sheet regions with concomitant hydrogen bond patterns. The tertiary structure of the protein was determined us ing 863 non-trivial proton-proton distance constraints, 14 hydrogen bo nd distance constraints and 55 phi and 25 chi(1) dihedral constraints. The structure that was obtained from distance geometry and energy ref inement contains three highly disordered loops as well as a disordered N- and C-terminal region. The remaining part of the structure is well defined with a root-mean-square deviation (rmsd) relative to the aver age of 0.09 +/- 0.02 nm for backbone atoms (residues 11-30, 37-50, 57- 69, 83-89). The protein comprises two identical domains, each containi ng a three-strand beta-sheet and two disulfide bonds: a 15-residue reg ion in each domain superimposes with 0.07 nm rmsd, measured on backbon e atoms. The solution structure is nearly identical to the crystal str ucture. It is in agreement with previous NMR data and, in combination with these data, supports the current model of procolipase micelle int eraction and the lipase activation by colipase.