MOLECULAR-CLONING AND EXPRESSION OF THE COAT PROTEIN GENES OF CF, A FILAMENTOUS BACTERIOPHAGE OF XANTHOMONAS-CAMPESTRIS PV CITRI

Particles of the filamentous bacteriophage Cf contain a major coat pro tein, the B protein, with a molecular weight of approximately 6,000. I n addition, a minor coat protein, the A protein, with a molecular weig ht of about 50,000, was also identified on sodium dodecyl sulfate-cont aining polyacrylamide gels. A 3.3 kbp HincII fragment derived from Cf genome was cloned into the expression plasmid pG308N, an E. coil plasm id which carries pL promoter. The recombinant plasmid pG33 and a serie s of deletion derivatives of pG33 were constructed and transformed int o E. coil DG116 for expression of phage Cf genes. The genes coding for A and B proteins of Cf were found on the 2.0 kbp EcoRI-HincII fragmen t. The complete nucleotide sequences of the 2.0 kbp EcoRI-HincII inser t were determined. The deduced amino acid sequence corresponds to a 62 -amino acid-residue polypeptide that has a calculated Mr of 6070 was i dentified as the B protein by SDS/PAGE and immunoblotting. Another ope n reading frame (ORF419) downstream of the B protein gene (ORF62) was found, and was shown to code for a polypeptide of 419 amino acids with a calculated Mr of 44,676 that exhibits considerable identity to the A protein.