Functional consequences of the open distal pocket of dehaloperoxidase-hemoglobin observed by time-resolved X-ray crystallography.
Biochemistry
; 52(45): 7943-50, 2013 Nov 12.
Article
em En
| MEDLINE
| ID: mdl-24116924
ABSTRACT
Using time-resolved X-ray crystallography, we contrast a bifunctional dehaloperoxidase-hemoglobin (DHP) with previously studied examples of myoglobin and hemoglobin to understand the functional role of the distal pocket of globins. One key functional difference between DHP and other globins is the requirement that H2O2 enter the distal pocket of oxyferrous DHP to displace O2 from the heme Fe atom and thereby activate the heme for the peroxidase function. The open architecture of DHP permits more than one molecule to simultaneously enter the distal pocket of the protein above the heme to facilitate the unique peroxidase cycle starting from the oxyferrous state. The time-resolved X-ray data show that the distal pocket of DHP lacks a protein valve found in the two other globins that have been studied previously. The photolyzed CO ligand trajectory in DHP does not have a docking site; rather, the CO moves immediately to the Xe-binding site. From there, CO can escape but can also recombine an order of magnitude more rapidly than in other globins. The contrast with DHP dynamics and function more precisely defines the functional role of the multiple conformational states of myoglobin. Taken together with the high reduction potential of DHP, the open distal site helps to explain how a globin can also function as a peroxidase.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Peroxidases
/
Hemoglobinas
/
Cristalografia por Raios X
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Estados Unidos