1,721,027 research outputs found
Probing Conformational Transitions in Interface α1β2 of Human Hemoglobin by Site-Directed Mutagenesis
No full textAiming at the study of the effect of Trp at the α1β2 interface of hemoglobin A (=Hb) on the stability of the tetrameric form of this protein and in order to introduce an additional probe for the T->R conformational transition, we have modelled by computer and produced in E. coli three Hb mutants: β37Trp->Thr, β37Trp->Thr/ α38Thr->Trp and α38Thr->Trp. An increase in the spectroscopic transition attributed to a Trp in the α1β2 interface of Hb was observed and a variation of the tetramer<->dimer equilibrium of the hemoglobin mutants was observed. The second observation is consistent with the behaviour expected from molecular modelling computations. © 1993, Elsevier B.V. All rights reserved
IS THE INTERNAL ELECTRON-TRANSFER THE RATE-LIMITING STEP IN THE CATALYTIC CYCLE OF CYTOCHROME-C-OXIDASE
No full textRECONSTITUTION OF CYTOCHROME-C-OXIDASE INTO PHOSPHOLIPID-VESICLES - EFFECT OF DETERGENTS
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ATP-INDUCED SPECTRAL PERTURBATION IN CYTOCHROME-OXIDASE - KINETIC ASPECTS AND ROLE OF CALCIUM-IONS
No full textELECTRON-TRANSFER TO THE BINUCLEAR CENTER IN CYTOCHROME-OXIDASE - CATALYTIC SIGNIFICANCE AND EVIDENCE FOR AN ADDITIONAL INTERMEDIATE
No full textExploring chromophore-protein interactions in fluorescent protein cmFP512 from Cerianthus membranaceus: X-ray structure analysis and optical spectroscopy
No full textAutofluorescent proteins of the GFP family all share the same three-dimensional -can fold; yet they exhibit widely different optical properties, arising either from chemical modification of the chromophore itself or from specific interactions of the chromophore with the surrounding protein moiety. Here we present a structural and spectroscopic characterization of the green fluorescent protein cmFP512 from Cerianthus membranaceus, a nonbioluminescent, azooxanthellate cnidarian, which has only ~22% sequence identity with Aequorea victoria GFP. The X-ray structure, obtained by molecular replacement at a resolution of 1. 35 Å, shows the chromophore, formed from the tripeptide Gln-Tyr-Gly, in a hydrogen-bonded cage in the center of an 11-stranded -barrel, tightly restrained by adjacent residues and structural water molecules. It exists in a neutral (A) and an anionic (B) species, with absorption/emission maxima at 392/460 (pH 5) and 503/512 nm (pH 7). Their fractional populations and peak positions depend sensitively on pH, reflecting protonation of groups adjacent to the chromophore. The pH dependence of the spectra is explained by a protonation mechanism involving a hydrogen-bonded cluster of charged/polar groups. Cryospectroscopy at 12 K was also performed to analyze the vibronic coupling of the electronic transitions
Time-resolved X-ray scattering as a tool to probe heme proteins structural dynamics in solution
No full textTime-resolved wide-angle X-ray scattering (TR-WAXS) is a recently developed technique allowing to probe global structural changes of proteins in solution. We have used TR-WAXS to investigate large conformational changes of heme proteins (wild-type and mutant hemoglobin, neuroglobin, etc.) that cannot take place when these macromolecules are in a crystalline environment. Our data revealed detailed information on kinetic and thermodynamic properties of the investigated proteins and demonstrate the potentiality of the TR-WAXS technique
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