title: Dual importance of positive charge in the C-terminal region of filamentous bacteriophage coat protein for membrane insertion and DNA-protein interaction in virus assembly.
abstract: Gene VIII encoding the procoat protein of the Class II filamentous bacteriophage Pf1 (infecting Pseudomonas aeruginosa) has been cloned and expressed in Escherichia coli and subjected to site-directed mutagenesis. The two positively charged residues clustered near the C-terminus, arginine-44 and lysine-45, were systematically converted to uncharged residues and serine-41 was converted to an arginine residue. Removal of positive charge in the C-terminal region of the molecule seriously impaired the ability of the procoat molecule to undergo insertion at the E. coli cell inner membrane, as manifested by the diminished processing of the N-terminal leader peptide. The basic amino acids near the C-terminus of the coat protein are also involved in neutralizing the negatively charged viral DNA during virus assembly. However, despite its additional positive charge, the S41R mutant protein was unable to participate in the assembly of Class I bacteriophage fd in E. coli. This dual requirement of positively charged residues in the C-terminal region of the coat protein for membrane processing and insertion and for electrostatic neutralization of the encapsidated DNA poses important constraints on the evolution of filamentous bacteriophages with two different helical symmetries.
authors.affiliation: Department of Biochemistry, University of Cambridge, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Greenwood
authors.forename: R N
authors.initials: RN
authors.lastname: Perham
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport; D002213:Capsid / Q000502:physiology* / Q000648:ultrastructure; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000502:physiology; D008565:Membrane Proteins / Q000502:physiology* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009024:Morphogenesis; D011499:Protein Processing, Post-Translational; D011550:Pseudomonas aeruginosa; D012995:Solubility; D013329:Structure-Activity Relationship; D014779:Virus Replication
chemical_list: D004268:DNA-Binding Proteins; D008565:Membrane Proteins