Five structural genes coding for the reaction center (RCj L, M, and H subunits and the two light-harvesting (LH) I polypeptides, B870a and B8706, have been mapped on two restriction fragments from the R-prime plasmid pRPS404. It has been recently shown that enhanced near-infrared fluo- The R-prime plasmid pRPS404 was generated by R-factor mobilization of the photosynthetic gene cluster from Rhodopseudomonas capsulata (1). This plasmid carries a 50-kilobase-pair (kb) insert of DNA indigenous to the R. capsulata chromosome that codes for most or all of the genes necessary for the differentiation of the oxidative-respiratory membrane into the photosynthetic membrane in response to low oxygen tension. The 50-kb gene cluster codes for biosynthetic enzymes required for carotenoid and bacteriochlorophyll biosynthesis and for the structural polypeptides of the reaction center (RC) and light-harvesting (LH) complexes. Approximately 15 genes have been mapped by a variety of techniques, including cotransduction of markers utilizing the gene transfer agent (2), marker-rescue using subclones of the R-prime (3), and R-prime site-directed transposon mutagenesis (4). Recently, 20 enhanced fluorescence mutants were isolated from a tetracycline suicide procedure, the chromatophore membranes were characterized by NaDodSO4/polyacrylamide gel electrophoresis, and the point mutations were mapped by marker-rescue using plasmid subclones of the Rprime (5). These studies showed that point mutations may cause enhanced LH II near-infrared fluorescence due to the loss or reduction of RC subunits or LH I polypeptides (or both). All of these point mutations map either to the BamHI C-EcoRI B fragment or to the EcoRI F fragment from the Rprime plasmid pRPS404. The restriction map of the R-prime plasmid has been recently aligned with the genetic map for genes encoding carotenoid and bacteriochlorophyll biosynthetic enzymes (3).Here we describe a preliminary analysis of the nucleotide sequence of the BamHI C-EcoRI B fragment (bearing rxcA) and the BamHI F fragment (contained within the EcoRI F fragment and bearing rxcB). Recently, the LH I polypeptides have been subjected to sequence analysis (M. H. Tadros, H. Zuber, and G. Drews, personal communication) and the RC L, M, and H subunit amino-terminal sequences are available from R. sphaeroides (6). These data have been used to scan the nucleotide sequence data to find the corresponding structural genes in the BamHI F and BamHI C-EcoRI B fragments. In this preliminary communication we report the complete nucleotide sequence of the structural genes for B870a and B870, [previously designated as the 12-and 8-kilodalton (kDa) LH I polypeptides (7), respectively]. Here we report only the position and deduced amino-terminal sequences of the RC subunits because fragmentary internal polypeptide data (not currently available) are required to verify the deduced RC polypeptide sequences.MATERIALS AND METHODS DNA Sequence and Computer Analyses. The nucleotide sequence of the BamHI F and BamHI C-EcoRI ...
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