Abstract
The physical properties and chemical structures of the filamentous phage Xf2 of Xanthomonas campestris pv. oryzae were clarified. The phage Xf2 was concentrated from enriched phage suspensin by differential centrifugation, purified by CsCl equilibrium density-gradient centrifugation and used for chemical analysis. The phage Xf2 was found to be composed of about 11% DNA and 89% of protein. The base composition of Xf2 DNA was adenine: guanine: cytosine: thymine=22.7:30.4:25.8:21.1, indicating high similarity to that of the X. campestris pv. oryzae phage Xf. Xf2 DNA was characterized as single-stranded one because of its noncomplementary base ratios and melting curve.
SDS polyacrylamide gel electrophoresis proved that Xf2 protein consisted of major and minor proteins. Major coat protein was found to consist of 43 amino acid residues, showing some differences from that of Xf and filamentous coliphages. Histidine, cystine and phenylalanie were absent and the content of hydrophobic amino acids was calculated at 15 molecules per one coat protein. The molecular weight of major coat protein of Xf2 determined by amino acid composition analysis was 4740 daltons, and that of minor coat protein determined by gel electrophoresis was 56, 000 daltons.
