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  • 1
    ISSN: 1573-5079
    Keywords: electron transfer ; proton transfer ; photosynthesis ; quinone ; reaction center ; site-specific mutagenesis ; suppressor mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two acidic residues, L212Glu and L213Asp, in the QB binding sites of the photosynthetic reaction centers of Rhodobacter capsulatus and Rhodobacter sphaeroides are thought to play central roles in the transfer of protons to the quinone anion(s) generated by photoinduced electron transfer. We constructed the site-specific double mutant L212Ala-L213Ala in R. capsulatus, that is incapable of growth under photosynthetic conditions. A photocompetent derivative of that strain has been isolated that carries the original L212Ala-L213Ala double mutation and a second-site suppressor mutation at residue M43 (Asn→Asp), outside of the QB binding site, that is solely responsible for restoring the photosynthetic phenotype. The Asp,Asn combination of residues at the L213 and M43 positions is conserved in the five species of photosynthetic bacteria whose reaction center sequences are known. In R. capsulatus and R. sphaeroides, the pair is L213Asp-M43Asn. But, the reaction centers of Rhodopseudomonas viridis, Rhodospirillum rubrum and Chloroflexus aurantiacus reverse the combination to L213Asn-M43Asp. In this respect, the QB site of the suppressor strain resembles that of the latter three species in that it couples an uncharged residue at L213 with an acidic residue at M43. These reaction centers, in which L213 is an amide, must employ an alternative proton transfer pathway. The observation that the M43Asn→Asp mutation in R. capsulatus compensates for the loss of both acidic residues at L212 and L213 suggests that M43Asp is involved in a new proton transfer route in this species that resembles the one normally used in reaction centers of Rps. virddis, Rsp. rubrum and C. aurantiacus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Using the ISO-DALT system for two-dimensional (2-D) electrophoresis and the TYCHO system for computer analysis of the resulting protein maps, we obtained high quality quantitative protein abundance data from Coomassie Brilliant Bluestained gels of mouse liver samples. High resolution gels allow more than 100 proteins to be measured with coefficients of variation less than 15 %. A comparison of results from two mouse strains (C57BL/6 and BALB/c) and the cross between them (BCF1) shows that a large number of qutive polymorphisms can be detected, and that, as expected, the amount of protein produced in the heterozygote is intermediate between the parental values. The system described is shown to be capable of reliably detecting decreases in protein abundance such as those expected to result from radiation-induced deletion of one copy of a gene. The implications of these results for the study of gene regulation are discussed in relation to applications in genetics, toxicology, and differentiation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Human plasma proteins separated by high-resolution two-dimensional electrophoresis have been electrophoretically transferred to sheets of nitrocellulose using a modification of the method of Towbin, Staehelin, and Gordon [8]. Although the proteins have been denatured in sodium dodecyl sulfate and separated into subunits, the nitrocellulose-bound molecules still react with appropriate specific antisera even after storage of the transfer in air at room temperature for 5 months. Of 25 proteins whose location in the pattern had been previously determined, 24 are specifically revealed on transfers of whole plasma patterns by appropriate antiserum. In addition, 6 previously unidentified proteins (prothrombin, C1s, C4γ, C1s inhibitor, Ig J-chain, and a1AP glycoprotein) have been identified in the pattern for the first time using the transfer technique. It therefore seems likely that a large majority of proteins (〉 96 % in this study) retain sufficient conformation throughout the analytical procedure (or can regain it easily afterwards) to be recognized immunologically. The transfer technique thus constitutes a generally useful immunological “third-dimension” in the high-resolution separation of proteins. Of three monoclonal antibodies similarly tested, none could detect antigen transferred to nitrocellulose from a two-dimensional gel, while each bound specifically to the appropriate antigen absorbed in native form to the nitrocellulose.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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