1bvm
|
SOLUTION NMR STRUCTURE OF BOVINE PANCREATIC PHOSPHOLIPASE A2, 20 STRUCTURES
OverviewOverview
Bovine pancreatic phospholipase A2 (PLA2), a small (13.8 kDa), Ca2+-dependent lipolytic enzyme, is rich in functional and structural, character. In an effort to examine its detailed structure-function, relationship, we determined its solution structure by multidimensional, nuclear magnetic resonance (NMR) spectroscopy at a functionally relevant, pH. An ensemble of 20 structures generated has an average root-mean-square, deviation (RMSD) of 0.62 +/- 0.08 A for backbone (N, Calpha, C) atoms and, 0.98 +/- 0.09 A for all heavy atoms. The overall structure shows several, notable differences from the crystal structure: the first three residues, at the N-terminus, the calcium-binding loop (Y25-T36), and the surface, loop (V63-N72) appear to be flexible; the alpha-helical conformation of, helix B (E17-F22) is absent; helix D appears to be shorter (D59-V63, instead of D59-D66); and the hydrogen-bonding network is less defined., These differences were analyzed in relation to the function of PLA2. We, then further examined the H-bonding network, because its functional role, or even its existence in solution has been in dispute recently. Our, results show that part of the H-bonding network (the portion away from, N-terminus) clearly exists in solution, as evidenced by direct observation, (at 11.1 ppm) of a strong H-bond between Y73 and D99 and an implicated, interaction between D99 and H48. Analyses of a series of mutants indicated, that the existence of the Y73.D99 H-bond correlates directly with the, conformational stability of the mutant. Loss of this H-bond results in a, loss of 2-3 kcal/mol in the conformational stability of PLA2. The, unequivocal identification and demonstration of the structural importance, of a specific hydrogen bond, and the magnitude of its contribution to, conformational stability, are uncommon to the best of our knowledge. Our, results also suggest that, while the D99.H48 catalytic diad is the key, catalytic machinery of PLA2, it also helps to maintain conformational, integrity.
About this StructureAbout this Structure
1BVM is a Single protein structure of sequence from Bos taurus. Active as Phospholipase A(2), with EC number 3.1.1.4 Full crystallographic information is available from OCA.
ReferenceReference
Structural analysis of phospholipase A2 from functional perspective. 1. Functionally relevant solution structure and roles of the hydrogen-bonding network., Yuan C, Byeon IJ, Li Y, Tsai MD, Biochemistry. 1999 Mar 9;38(10):2909-18. PMID:10074343
Page seeded by OCA on Tue Nov 20 11:57:15 2007