2ND-SITE SUPPRESSORS OF A COLD-SENSITIVE EXTERNAL SCAFFOLDING PROTEINOF BACTERIOPHAGE-PHI-X174

This report describes the isolation and characterization of second-sit e suppressors of a cold-sensitive (cs) external scaffolding protein, g pD, of bacteriophage phiX174. Seven genetically distinct suppressors w ere isolated. Six of them are located in gene F which encodes the majo r coat protein of the virus. The seventh is located in gene J which en codes the DNA-binding protein. A subset of the suppressors are trans-a cting. These second-site suppressors do not exhibit allele specificity ; they are able to suppress defects associated with a csD protein for which they were not selected. The initial characterization of the seco nd-site suppressors and their locations within the major coat protein suggest that the mechanism of suppression may involve both structural and stoichiometric phenomena.