Transfection: Enhancement by assembly protein of bacteriophage R17

Abstract

Assembly protein was isolated by DEAE cellulose chromatography from disrupted R17 bacteriophage and reconstituted with purified R17 phage RNA. Following reconstitution, 125I labeled assembly protein co-sediments with 27S R17 phage RNA in a sucrose gradient. SDS-polyacrylamide gel analysis of the 27S 125I labeled protein-RNA complex confirmed that assembly protein was the only phage protein associated with the RNA. The specific infectivity (PFU/μg RNA) of the R17 phage RNA-assembly protein complex was 35-fold greater than that of R17 phage RNA when assayed on Escherichia coli spheroplasts. Infectivity of both preparations was destroyed by treatment with pancreatic ribonuclease A. Furthermore, the assembly protein-RNA complex was infectious for intact cells whereas phage RNA was not infectious. Infectivity of this 27S complex for intact cells was totally eliminated by pretreatment with ribonuclease.