Linked Life Data

8504086

Source:http://linkedlifedata.com/resource/pubmed/id/8504086

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
1993-7-6
pubmed:abstractText
The 1H NMR spectrum of the cyanomet complex of the sperm whale His[E7]Val myoglobin (Mb) point mutant has been analyzed by 2D methods to yield the assignments for the active site residues, including the substituted Val E7. The dipolar shifted proximal residues are used to quantitatively locate the magnetic axes for the paramagnetic susceptibility tensor in the molecular framework. The orientation of the major axis, which correlates with the ligand tilt, is approximately 15 degrees from the heme normal, as found in wild-type (WT) Mb, but is tilted in a direction rotated approximately 40 degrees toward the heme gamma-meso position with respect to WT and similar to that in the His[E7]Gly mutant [Rajarathnam, K., La Mar, G. N., Chiu, M., & Sligar, S. G. (1992) J. Am. Chem. Soc. 114, 9048-9058]. The altered direction of an unchanged tilt angle for the Fe+3-CN unit is shown to be qualitatively consistent with earlier computations of the potential energy surface for MbCO [Kuriyan, J., Wilz, S., Karplus, M., & Petsko, G. A. (1986) J. Mol. Biol. 192, 133-154]. It is concluded that His E7 does not significantly contribute to the ligand tilt but strongly influences the direction of tilt. Deviations between observed and predicted dipolar shifts for the E-helix backbone protons and perturbed patterns of their respective nuclear Overhauser effect between the E-helix and the heme 1,8-methyls are separately analyzed for movement of the E-helix and agree on a translation of the E-helix of the order of 0.8 A in a direction toward the iron. The discrepancy between observed and predicted dipolar shifts for Phe CD1 indicates a approximately 0.5-A movement by the ring parallel to the heme and towards the E-helix. The E-helix and Phe CD1 movements are consistent with a contraction of the pocket to fill the space created by the His-->Val substitution. The correlation between the observed dipolar shifts of the substituted Val E7 side chain and those calculated as a function of rotation of the residue with and without movement of the E-helix confirm the movement of the E-helix and allow a quantitative description of the Val orientation. It is concluded that the dipolar field of the paramagnetic susceptibility tensor provides an important quantitative constraint for defining the heme cavity structure in cyanomet complexes of distal point mutants of myoglobin and hemoglobin.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
32
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5670-80
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Solution structure determination of the heme cavity in the E7 His-->Val cyano-met myoglobin point mutant based on the 1H NMR detected dipolar field of the iron: evidence for contraction of the heme pocket.
pubmed:affiliation
Department of Chemistry, University of California, Davis 95616.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.