1ppt
From Proteopedia
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X-RAY ANALYSIS (1.4-ANGSTROMS RESOLUTION) OF AVIAN PANCREATIC POLYPEPTIDE. SMALL GLOBULAR PROTEIN HORMONE
Overview
The crystal structure of avian pancreatic polypeptide (aPP), a 36-residue, polypeptide with some hormonal properties, has been determined by using, single isomorphous replacement and anomalous scattering to 2.1-A, resolution. The phases were extended to 1.4-A resolution by using a, modified tangent formula. The molecule contains two regions of secondary, structure-an extended polyproline-like helix (residues 1-8) and an, alpha-helix (residues 14-31)-that run roughly antiparallel. The packing, together of nonpolar groups from these regions gives the molecule a, hydrophobic core in spite of its small size. The aPP molecules form a, symmetrical dimer in the crystal stabilized principally by interlocking of, nonpolar groups from the alpha-helices. The aPP dimers are crosslinked by, coordination of Zn(2+); three aPP molecules contribute ligands to each, zinc. The coordination geometry is a distorted trigonal bipyramid. The, properties of the aPP molecule in solution are consistent with, expectations based on the crystal structure. The aPP molecule has several, general features in common with the pancreatic hormones insulin and, glucagon. All three hormones have complex mechanisms for self-association., Like insulin, aPP seems to have a stable monomeric structure but its, biological activity seems to depend on the more flexible COOH-terminal, region analogous to the flexible NH(2)-terminal region of glucagon.
About this Structure
1PPT is a Single protein structure of sequence from Meleagris gallopavo with ZN as ligand. Full crystallographic information is available from OCA.
Reference
X-ray analysis (1. 4-A resolution) of avian pancreatic polypeptide: Small globular protein hormone., Blundell TL, Pitts JE, Tickle IJ, Wood SP, Wu CW, Proc Natl Acad Sci U S A. 1981 Jul;78(7):4175-4179. PMID:16593056
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