Ligation Tunes Protein Reactivity in an Ancient Haemoglobin: Kinetic Evidence for an Allosteric Mechanism in Methanosarcina acetivorans Protoglobin
Abstract: Protoglobin from Methanosarcina acetivorans (MaPgb) is a dimeric globin with peculiar structural properties such as a completely buried haem and two orthogonal tunnels connecting the distal cavity to the solvent. CO binding to and dissociation from MaPgb occur through a biphasic kinetics. We show that the heterogenous kinetics arises from binding to (and dissociation from) two tertiary conformations in ligation-dependent equilibrium. Ligation favours the species with high binding rate (and low dissociation rate). The equilibrium is shifted towards the species with low binding (and high dissociation) rates for the unliganded molecules. A quantitative model is proposed to describe t…
The nerve hemoglobin of the bivalve mollusc Spisula solidissima
Abstract Members of the hemoglobin (Hb) superfamily are present in nerve tissue of several vertebrate and invertebrate species. In vertebrates they display hexacoordinate heme iron atoms and are typically expressed at low levels (μm). Their function is still a matter of debate. In invertebrates they have a hexa- or pentacoordinate heme iron, are mostly expressed at high levels (mm), and have been suggested to have a myoglobin-like function. The native Hb of the surf clam, Spisula solidissima, composed of 162 amino acids, does not show specific deviations from the globin templates. UV-visible and resonance Raman spectroscopy demonstrate a hexacoordinate heme iron. Based on the sequence analo…
Characterization of the Heme Pocket Structure and ligand binding kinetics of non-symbiotic hemoglobins from the model legume Lotus japonicus
14 Pags.- 6 Figs. This article is part of the Research Topic: Advances in legume research ( http://journal.frontiersin.org/researchtopic/4288/advances-in-legume-research ). Copyright of the Authors through a Creative Commons Attribution License. This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.