Linked Life Data

2168882

Source:http://linkedlifedata.com/resource/pubmed/id/2168882

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
27
pubmed:dateCreated
1990-10-18
pubmed:abstractText
The proton NMR spectra of ferricytochrome c' from Rhodopseudomonas palustris, Rhodospirillum molischianum, Rhodospirillum rubrum, and Chromatium vinosum have been investigated for the purpose of further elucidating the common spectral and/or structural properties for this subclass of cytochromes in the acidic and alkaline forms, and to characterize in detail the dynamics and structural basis for this acid in equilibrium with alkaline transition. The identification of strongly upfield-shifted meso-H peaks in all but C. vinosum ferricytochrome c' at weakly acidic to neutral pH is consistent with, but not proof for, S = 3/2 character for the spin state of C. vinosum, but argues for primarily S = 5/2 character for the other three proteins. Hence, we conclude that the quantum mechanically mixed S = 3/2, S = 5/2 spin ground state of neutral pH C. vinosum ferricytochrome c' is an anomaly rather than a characteristic of this class of proteins. The 1H NMR spectra of ferricytochromes c' at alkaline pH again exhibit strong similarities among all members except that for C. vinosum. Two pK values are observed for ferricytochrome c' for R. molischianum and C. vinosum, of which the higher value pK is accompanied by significant line broadening, as found earlier for the proteins from both R. rubrum and R. palustris. Detailed analysis of the exchange line broadening for all four proteins reveals that hydrolysis is the rate-limiting step, with base catalysis occurring at about the same rate in the diffusion control limit for all four proteins. The variable first order dissociation rates of the alkaline species reveal differential stabilities of that species in the order R. palustris greater than R. molischianum greater than R. rubrum much greater than C. vinosum. The rates of exchange of the axial His imidazole labile proton was determined by linewidth and saturation transfer analysis and shown to occur via base catalysis at the same diffusion control rate as found for the acid----alkaline transition for the oxidized protein, and support the proposal that the acid----alkaline transition involves simply the abstraction of a proton from the neutral His imidazole to yield an imidazolate.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
25
pubmed:volume
265
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
16173-80
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1990
pubmed:articleTitle
Proton NMR study of the comparative electronic/magnetic properties and dynamics of the acid in equilibrium with alkaline transition in a series of ferricytochromes c'.
pubmed:affiliation
Department of Chemistry, University of California, Davis 95616.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't