The membrane location of the B890-complex from Rhodospirillum rubrum and the effect of carotenoid on the conformation of its two apoproteins exposed at the cytoplasmic surface

Brunisholz, RenéA.; Zuber, Herbert; Valentine, Jane L.; Lindsay, J. Gordon; Woolley, Kevin J.; Cogdell, Richard J.

doi:10.1016/0005-2728(86)90141-6

Cited by 43 publications

(25 citation statements)

References 20 publications

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“…The amino acid substitution aTrpSTyr, for example, impairs specifically the carotenoid incorporation into the antenna aggregate without changing other structural parameters. The characteristics of this phenotype thus support the postulated interaction between the carotenoid and the N-terminal hydrophobic region of the a polypeptide [13]. A similar, though weaker, effect on carotenoid binding was observed in the mutant aAspl2Glu.…”

Section: Discussionsupporting

confidence: 71%

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Single amino acid substitutions in the B870 α and β light‐harvesting polypeptides of Rhodobacter capsulatus

Babst

Albrecht

Wegmann

et al. 1991

European Journal of Biochemistry

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To obtain information on the structural and functional role of highly conserved amino acid residues in the B870 and light-harvesting polypeptides of Rhodobucter cupsulutus, site-directed mutagenesis was performed. 18 mutants with single amino acid substitutions at nine different positions in the B870 antenna polypeptides were prepared in a B800-850-lacking strain. The characterization of the resulting phenotypes was based on a quantification of the core-complex elements (reaction center, light-harvesting polypeptides, bacteriochlorophyll u and carotenoid) and the core-complex spectral characteristics (absorption maximum, absorption coefficient and fluorescence intensity). These data generally showed that strong structural effects were caused by the amino acid substitutions. Thus, the three tryptophan exchanges at the position cr8 resulted in either the absence of a core complex (aTrp8-+Leu), the absence of the core antenna (aTrpS+Ala) or a reduction in the carotenoid content (aTrp8-tTyr). Likewise, the mutants aProl3Gly (i.e. aProl3-+Gly), PGlylOVal and aPhe23Ala demonstrated an abnormal protein/pigment ratio in the core antenna, while a drastically reduced antenna size resulted from the amino acid exchange PArg45Asp. In contrast to the structural effects, the absorption maxima and the fluorescence intensities of the mutant antennae differed only slightly from the wild type. The strongest blue shift of the bacteriochlorophyll u (8-11 nm) was induced by substitutions of the Trp at position a43 (aTrp43-+Ala, Leu or Tyr). Contrary to the other spectral effects, the absorption coefficient of bacteriochlorophyll u was strongly influenced by the amino acid substitutions and varied by 1.6-times less (pArg45Asp) and 1.3-times greater (aPhe25Ala) than normal. The antenna-free mutant, aTrpSAla, yielded a high rate of B800-850 revertants during phototrophic growth, indicating a direct energy transfer from the B800-850 antenna to the reaction center in these strains. Although conditions for growth were generally observed to influence phenotypic expression, the structural as well as spectral effects were demonstrated to differ to the greatest extent between chemotrophically grown and phototrophically grown cells.Rhodobacter capsulatus is a Gram-negative, photosynthetic bacterium and belongs to the group of non-sulfur purple bacteria [l]. The photosynthetic system of Rb. cupsulutus consists of two functional units; the light-harvesting antenna which absorbs light energy and transfers it to the reaction center (RC) and the RC which applies this energy to produce a proton gradient across the membrane. The antenna is an intramembranous protein-pigment complex. Two antenna complexes, the B870 and B800-850 complexes, have been structurally and spectroscopically distinguished in Rb. cupsulutus, and these are subsequently named according to their absorption peaks in the near-infrared region (Q, band). The B870 antenna forms a fixed-size aggregate with the RC, called the core complex. This complex is surrounded by the B800-850 comple...

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Section: Discussionsupporting

confidence: 71%

“…capsulutus contains two light-harvesting polypeptides (LHP), a ( M , 6588) and P the core antenna of purple bacteria [13]. The molar ratio of polypeptide/chlorophyll/carotenoid was determined to be 1 : l : l [14].…”

Section: Single Amino Acid Substitutions In the B870mentioning

confidence: 99%

Single amino acid substitutions in the B870 α and β light‐harvesting polypeptides of Rhodobacter capsulatus

Babst

Albrecht

Wegmann

et al. 1991

European Journal of Biochemistry

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“…Exchange of Trp-8 of the LHI a protein of R. capsulatus to Ala reduced drastically the amount of the LHI a protein integrated into the membrane (42). If carotenoids are associated with the aromatic structure of Trp and are involved in a conformational change of the LHI a protein (as postulated in reference 7), and if this change is necessary for insertion of the protein into the ICM, this would explain why the Ala-8 LHI a protein could not efficiently contact the membrane (42).…”

Section: Discussionmentioning

confidence: 91%

“…The B890 ,B protein, however, was always accessible to proteinase K whether carotenoids were bound or not. Brunisholz et al (7) concluded that the B890 a protein undergoes a conformational change in the presence of carotenoids. The B890 a polypeptide of R. rubrum has an Arg-Ile-Trp stretch at about the same position as the Lys-Ile-Trp stretch of the LHI a protein of R. capsulatus (50).…”

Section: Discussionmentioning

confidence: 99%

Characterization of LHI- and LHI+ Rhodobacter capsulatus pufA mutants

1992

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The NH2 termini of light-harvesting complex I (LHI) polypeptides a and ,B of Rhodobacter caus are thought to be involved in the assembly of the LHI complex. For a more detailed study of the role of the NH2-terminal segment of the LHI a protein in insertion into the intracytoplasmic membrane (ICM) of R. ca,psulaus, amino acids 6 to 8, 9 to 11, 12 and 13, or The LHI a and 1 polypeptides are present in a 1:1 ratio. The LHI apoproteins are integral proteins of the intracytoplasmic membrane (ICM) and span the membrane once with * Corresponding author. a central hydrophobic domain (51-53). The NH2 terminus of the LHI a polypeptide is located in the cytoplasm and has a short hydrophobic central part of amino acid residues flanked by positively charged residues which are next to a conserved proline (51, 52). The LHI a protein is inserted into the ICM in wild-type amounts only in the presence of the LHI 1 protein (43). The LHI 1 protein, however, has a negatively charged NH2 terminus and is able to integrate temporarily into the membrane in the absence of the LHI a protein (43). The LHI 13 protein was observed to be inserted earlier into the ICM than was the LHI a protein (43).The described structures and features of the LHI a and 1 polypeptides are conserved among several species of the genus Rhodospirillaceae (50). Two highly conserved amino acid residues (Trp-8 and Pro-13) are present in the NH2 terminus of the LHI a polypeptide (50). The aromatic structure of the Trp at position 8 seems to be of importance for the insertion of the LHI a polypeptide into the ICM (42). The conservative amino acid residue Pro-13, however, seems to be necessary for keeping the LHI 1 partner polypeptide in the membrane (42).Deletions or insertions have been introduced into the NH2 terminus of the LHI a protein to obtain more information on the structural requirements for the membrane insertion of the LHI a protein and the assembly of both LHI proteins into a functional complex. The construction and characterization of R capsulatus LHI-strains containing a mutated LHI a polypeptide are described in this report. Additionally, LHI+ revertant strains of one LHI-mutant strain are characterized.3030

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“…The basic structure of all LHs is thought to be a heterodimer of the small a and polypeptides (5-10 kDa) that bind pigments in a specific stoichiometry distinctive of LH1 or LH2. Sequence analysis and circular dichroism measurements of antenna complexes of purple-nonsulfur bacteria suggest that each LH1 or LH2 antenna polypeptide spans the membrane once in the form of an a-helix (Cogdell & Scheer, 1985;Brunisholz et al, 1986). The limited biochemical data on purple-sulfur organisms (members of the Chromatiaceae) indicate subunit homology at the level of function and of primary sequence (Bissig et al, 1990;Kerfeld et al, manuscripts submitted and in prep.…”

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confidence: 99%

Crystallization of two integral membrane pigment–protein complexes from the purple‐sulfur bacterium Chromatium purpuratum

1993

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The membrane location of the B890-complex from Rhodospirillum rubrum and the effect of carotenoid on the conformation of its two apoproteins exposed at the cytoplasmic surface

Cited by 43 publications

References 20 publications

Single amino acid substitutions in the B870 α and β light‐harvesting polypeptides of Rhodobacter capsulatus

Single amino acid substitutions in the B870 α and β light‐harvesting polypeptides of Rhodobacter capsulatus

Characterization of LHI- and LHI+ Rhodobacter capsulatus pufA mutants

Crystallization of two integral membrane pigment–protein complexes from the purple‐sulfur bacterium Chromatium purpuratum

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