R L Duda — Page 2 | PubMed Health

PubMed1985

Mass distribution of a probable tail-length-determining protein in bacteriophage T4.

Analysis of dark-field scanning transmission electron micrographs of unstained freeze-dried specimens established that the interior of the intact bacteriophage T4 tail tube contains extra density that is missing in tubes artificially emptied by treatment with 3 M guanidine hydrochloride. The mass of the tail tube is 3.1 X 10(6) daltons, and the central channel is 3.2 nm in diameter. Quantitative analysis of the density data is consistent with the presence of up to six strands of a protein molecule in the central channel that could serve as the template or ruler structure that determines the length of the bacteriophage tail and that could be injected into the cell with the phage DNA.

Escherichia coli↗

PubMed1982

Evidence for an internal component of the bacteriophage T4D tail core: a possible length-determining template.

The length of the T4 tail is precisely regulated in vivo at the time of polymerization of the tail core protein onto the baseplate. Since no mutations which alter tail length have been identified, a study of in vivo-assembled tail cores was begun to determine whether the structural properties of assembled cores would reveal the mechanism of length regulation. An assembly intermediate consisting of a core attached to a baseplate (core-baseplate) was purified from cells infected with a T4 mutant in gene 15. When core-base plates were treated with guanidine hydrochloride, cores were released from baseplates. The released cores had the same mean length as cores attached to baseplates. Electron micrographs of these cores showed partial penetration of negative stain into one end, and, at the opposite end, a modified tip which often appeared as a short fiber projecting from the core. When cores were purified and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, two minor proteins and the major core protein were detected. One minor protein, the product of gene 48 (gp48), was present in at least 72% of the amount found in core-baseplates, relative to the amount of the major core protein. These findings suggest that cores contain a fibrous structure, possibly composed of gp48, which may form a "ruler" that specifies the length of the T4 tail.

Guanidine↗