1mhl
From Proteopedia
CRYSTAL STRUCTURE OF HUMAN MYELOPEROXIDASE ISOFORM C CRYSTALLIZED IN SPACE GROUP P2(1) AT PH 5.5 AND 20 DEG C
Overview
A 3-A-resolution X-ray crystal structure of canine myeloperoxidase has previously revealed the overall structure of the molecule, including the polypeptide backbone conformation, but did not provide an unambiguous structure for the covalently bound heme. A higher resolution (2.28 A) X-ray crystal structure of human myeloperoxidase has now shown that the heme is a novel derivative of protoporphyrin IX in which three ring substituents form covalent bonds with amino acid side chains in the protein. Modified methyl groups on pyrrole rings A and C form ester linkages with glutamate 242 and aspartate 94, while a covalent bond between the vinyl group on ring A and the sulfur atom of methionine 243 results in a sulfonium ion linkage. The heme tetrapyrrole ring also shows considerable distortion from the planar conformation seen in most heme-containing proteins. The observed bending appears to result from these covalent bonds between diametrically opposed pyrrole rings A and C and the protein. Sequence comparisons suggest that the two ester linkages to the heme may also occur in other homologous mammalian peroxidases, but that the sulfonium ion linkage may be a unique feature of myeloperoxidase.
About this Structure
1MHL is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Structure of the green heme in myeloperoxidase., Fenna R, Zeng J, Davey C, Arch Biochem Biophys. 1995 Jan 10;316(1):653-6. PMID:7840679 Page seeded by OCA on Sat May 3 01:02:27 2008
