THE RGD SEQUENCE IN PHAGE-PHI-29 TERMINAL PROTEIN IS REQUIRED FOR INTERACTION WITH PHI-29-DNA-POLYMERASE

The RGD (Arg-Gly-Asp) motif functions as a recognition site for adhesi ve proteins responsible for a number of cell-cell interactions. Certai n viruses use this sequence as a receptor-binding site by interaction with cellular integrins. To elucidate the role of the RGD sequence of the empty set 29 terminal protein (TP), seven modified TPs were genera ted by site-directed mutagenesis. Most of the TP mutants were not effi ciently used as primers, leading to a reduction of the TP-dAMP complex formation in the presence of the empty set 29 TP-DNA template. Moreov er, these mutant TPs were poorly deoxyadenylylated by empty set 29 DNA polymerase in the absence of template. Analysis of primer TP/DNA poly merase complex formation showed that the modified TPs were affected in the formation of the heterodimeric complex. These results indicate th at the RGD sequence present in empty set 29 TP is primarily involved i n interaction with the viral DNA polymerase. (C) 1998 Academic Press.