Linked Life Data

11087382

Source:http://linkedlifedata.com/resource/pubmed/id/11087382

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
46
pubmed:dateCreated
2000-12-12
pubmed:abstractText
The unicellular protozoan Paramecium caudatum contains a monomeric hemoglobin (Hb) that has only 116 amino acid residues. This Hb shares the simultaneous presence of a distal E7 glutamine and a B10 tyrosine with several invertebrate Hbs. In the study presented here, we have used ligand binding kinetics and resonance Raman spectroscopy to characterize the effect of the distal pocket residues of Paramecium Hb in stabilizing the heme-bound ligands. In the ferric state, the high-spin to low-spin (aquo-hydroxy) transition takes place with a pK(a) of approximately 9.0. The oxygen affinity (P(50) = 0.45 Torr) is similar to that of myoglobin. The oxygen on- and off-rates are also similar to those of sperm whale myoglobin. Resonance Raman data suggest hydrogen bonding stabilization of bound oxygen, evidenced by a relatively low frequency of Fe-OO stretching (563 cm(-1)). We propose that the oxy complex is an equilibrium mixture of a hydrogen-bonded closed structure and an open structure. Oxygen will dissociate preferentially from the open structure, and therefore, the fraction of open structure population controls the rate of oxygen dissociation. In the CO complex, the Fe-CO stretching frequency at 493 cm(-1) suggests an open heme pocket, which is consistent with the higher on- and off-rates for CO relative to those in myoglobin. A high rate of ligand binding is also consistent with the observation of an Fe-histidine stretching frequency at 220 cm(-1), indicating the absence of significant proximal strain. We postulate that the function of Paramecium Hb is to supply oxygen for cellular oxidative processes.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
39
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
14330-40
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Ligand binding in the ferric and ferrous states of Paramecium hemoglobin.
pubmed:affiliation
Department of Physiology and Biophysics, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA. tdas@aecom.yu.edu
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't