TITLE	Adsorption protein of filamentous bacteriophage fXo from Xanthomonas oryzae
AUTHOR	Tzu-Jun Liu Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan Bih-Yuh You Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan Tsai-Tien Tseng Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan Nien-Tsung Lin Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan Ming-Te Yang Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan Yi-Hsiung Tseng* Institute of Molecular Biology, National Chung Hsing University, Taichung 402, Taiwan
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ABSTRACT	fXo, Xf, fLf, fXv, and Cf are filamentous bacteriophages isolated in Taiwan. Both fXo and Xf specifically infect Xanthomonas oryzae pv. oryzae, and fLf, fXv, and Cf specifically infect X. campestris pv. campestris, X. campestris pv. vesicatoria, and X. campestris pv. citri, respectively. In this study, the fXo gene III (gIII) encoding the adsorption protein (pIII) was cloned by probing with the fLf gIII. Sequence analysis revealed that the fXo gIII is 1,023-nt long and able to encode a pre-protein of 340 aa (35,337 Da), with structural features typical of filamentous phage adsorption proteins: an N-terminal signal sequence (18 aa), a central region (90 aa) containing 38 glycine, 29 aspartic acid and 19 histidine residues, and a C-terminal membrane-anchoring domain (17 aa). The fXo pIII purified from the phage particles migrated as a 42-kDa band in SDS-polyacrylamide gel, which is substantially larger than that deduced from the nucleotide sequence, presumably due to the presence of the long stretch of charged residues in the central region. The fXo pIII could cross-react with the antiserum specific to fLf pIII, which also cross-reacts with fXv pIII. Like the situations in fLf and fXv, the pIIIs of fLf and fXo are also interchangeable. The gIII and the flanking regions of fLf, fXv and fXo are highly homologous and similar in size, but fXo has a genome (7.6 kb) larger than that of fLf (6.0 kb) and fXv (6.4 kb), suggesting that fXo is able to accommodate more genes and/or have longer intergenic regions in the remaining part of the genome. Difference in sizes between the pIIIs indicates that fXo and Xf, which has a predicted pre-pIII of 488 aa (51,036 Da), are distinct phages.
KEYWORD	Adsorption protein; Aspartic acid and histidine; Gene III; High content of glycine; Membrane-anchoring domain; Signal sequence; Xanthomonas;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 42 Number 3 July 2001, page 193-199, 7 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China