PMID:2150914
| Citation |
Xue, MQ and Black, LW Role of the major capsid protein of phage T4 in DNA packaging from structure-function and site-directed mutagenesis studies. J. Struct. Biol. 104:75-83 |
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| Abstract |
Heat cleavage of asp-pro peptide bonds was used to probe the primary structures of the Phage T4 major capsid protein precursor, gp23, its mature capsid form gp23*, and a DNA-dependent ATPase, called capsizyme. This analysis suggests that capsizyme is a gp23** resulting from the N-terminal processing found in gp23* as well as shortening at the C-terminus. Photoaffinity labeling with Azido-ATP and BrU-DNA, followed by heat cleavage, suggests binding sites for these compounds toward the C-terminus of gp23**, suggesting localization of functions within the gp23 primary sequence. Site-directed mutagenesis experiments were targeted therefore to the C-terminal end of g23 as well as to its processing sites. N-terminal processing site modification supports the consensus gp21 proteinase cleavage rule, whereas mutagenesis at the C-terminus suggests that the C-terminal alteration is unlikely to result from a gp21-morphogenesis proteinase cleavage. Amino acid replacements in gp23 at newly introduced amber sites reveal a new g23 mutant phenotype, defective partially DNA-filled heads, in support of the hypothesis that gp23 and its products function directly in the DNA packaging mechanism. |
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| Keywords |
Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Adenosine Triphosphate/metabolism; Amino Acid Sequence; Base Sequence; Binding Sites; Capsid/genetics; Capsid/metabolism; Capsid/ultrastructure; Capsid Proteins; DNA, Viral/genetics; DNA, Viral/metabolism; DNA, Viral/ultrastructure; Escherichia coli/genetics; Escherichia coli/metabolism; Hot Temperature; Microscopy, Electron; Molecular Sequence Data; Mutagenesis, Site-Directed; Oligonucleotide Probes; Protein Precursors/genetics; Protein Precursors/metabolism; T-Phages/genetics; T-Phages/metabolism; T-Phages/ultrastructure |
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