Structure and Properties of the Rapidly Sedimenting Replicating Complex of Staphylococcal Phage K DNA

. * SUMMARY Rapidly sedimenting complexes (RSCs) of replicating phage K DNA, isolated by rate zonal centrifugation in sucrose gradients, contain bacterial membrane lipids and protein. During the first half of the latent period the number of DNA molecules in a RSC increased from 1 to about 27. Digestion by Pronase caused the complexes to dissociate and release virion lengths of DNA which sedimented slowly like free mature DNA. RSCs.treated with SDS disintegrated and released tangled DNA molecules, each about one virion length in size, but these structures retained their fast sedimentation characteristic. Chloramphenicol (CM) at 100 pg/ml did not completely inhibit complex formation or DNA replication, indicating that pre-existing host proteins were involved in these processes. CM reduced DNA replication by 50 to 80%. It is concluded that phage K DNA replicates attached to the cytoplasmic membrane of the host.