Abstract
The C and D proteins from bacteriophage fd and fl have been purified and characterized. Since the DNA sequence is known, the amino acid composition of these purified proteins indicated that they are coded for by the phage, the C protein being the product of Gene IX and the D protein specified by Gene VI. The molecular weights of the C and D proteins were calculated from the DNA sequences to be 3,650 and 12,350, respectively. These values are close to the molecular weights observed after polyacrylamide gel electrophoresis of the proteins in sodium dodecyl sulfate. Since the C and D proteins can be selectively labeled with radioactive cysteine and arginine, it was possible to estimate the number of the C and D protein molecules relative to the number of A protein molecules which had been accurately determined in previous studies. Based on these results, the average phage particle contains 5 A, 5 D, and 10 C protein molecules.
Highlights
These values are close to the molecular weights observed after polyacrylamide gel electrophoresis of the proteins in sodium dodecyl sulfate
Over the years there have been several reports of the presence of other low molecular weight proteins associated with the virion [1,5,6,7]
Simons et al [8],using radiochemical techniques, have identified two proteins inM13 which were associated with the phage particles and had apparent molecular weights of3,500 and 11,500, respectively
Summary
Until recently there was direct evidence for only two capsid proteins, the major coat (B) and a minor coat (A) protein in the fdamentous viruses (fd, M13, and fl)(for virus, see Refs. 1-4). Over the years there have been several reports of the presence of other low molecular weight proteins associated with the virion [1,5,6,7]. Simons et al [8],using radiochemical techniques, have identified two proteins inM13 which were associated with the phage particles and had apparent molecular weights of500 and 11,500, respectively. Studieson the morphogenesis of filamentous phages require the isolation of phage-specific proteins in chemically significant quantities. This will allow specific antibodies to be prepared for determination of the location and time of appearance of these minor proteins. Goldsmith and Konigsberg [6] and Woolford et al [7] used suchan approach to definitively establish the identity of the A proteinas the product of Gene I11and tolocate this proteinat one end of the fd and fl virions
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