Solution Structure of Porcine Pancreatic Procolipase as Determined from ¹H Homonuclear Two‐Dimensional and Three‐Dimensional NMR

Abstract

Procolipase is the precursor of colipase, which acts as protein cofactor for the activity of pancreatic lipase. The solution structure of procolipase has been determined by 1H NMR using two‐ and three‐dimensional measurements. The secondary structure determination identified two separate three‐stranded β‐sheet regions with concomitant hydrogen bond patterns. The tertiary structure of the protein was determined using 863 non‐trivial proton–proton distance constraints, 14 hydrogen bond distance constraints and 55 Ø and 25 χ1 dihedral constraints. The structure that was obtained from distance geometry and energy refinement 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 average 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 containing a three‐strand β‐sheet and two disulfide bonds: a 15‐residue region in each domain superimposes with 0.07 nm rmsd, measured on backbone atoms. The solution structure is nearly identical to the crystal structure. It is in agreement with previous NMR data and, in combination with these data, supports the current model of procolipase micelle interaction and the lipase activation by colipase.

Structure and Orientation of Pancreatic Colipase in a Lipid Environment: PM-IRRAS and Brewster Angle Microscopy Studies

“…Colipase is a small, amphipathic, and rather flat protein which lacks extensive secondary structure. It is made of a central region of two β-sheets held together by disulfide bonds, with four fingershaped regions connected by type I β-turns protruding from this central region and an N-terminal region with no apparent secondary structure (no electron density in the X-ray structure) (10)(11)(12). Two short stretches of R-helical residues are observed, one (residues [22][23][24] in the first finger (residues [14][15][16][17][18][19][20][21][22][23] and the other one in the last finger (residues 76-80).…”