Biology ETDs

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The structural proteins of Micrococcus lysodeikticus bacteriophage N1 were studied by SDS-urea polyacrylamide gel electrophoresis. Electrophoretic analysis of highly purified virions revealed that N1 phage is composed of six structural polypeptides which were designated VP1 through VP6. Molecular weights of the virion polypeptides were estimated to be 103,000 (VP1), 76,000 (VP2), 66,000 (VP3), 51,000 (VP4), 26,000 (VP5), and 16,750 (VP6) daltons. Quantitative analysis of electropherograms of N1 indicated that VP4, VPS, and VP6 are major components of the virion representing 46%, 29%, and 19% of the weight of the virion protein, respectively. The three minor polypeptides VP1, VP2, and VP3 each represent approximately 2% of the virion protein. These six structural polypeptides account for approximately 19% of the coding capacity of the N1 phage genome. Sonication of purified N1 phage disrupted the virus into empty heads, ghosts with abnormally long tails, and a population of tails of heterogenous lengths. In vitro end-to-end polymerization of tails or tail fragments was apparently a factor contributing to these abnormalities in phage tail lengths. Empty heads and ghosts with abnormally long tails were isolated by sucrose gradient centrifugation and proved to be useful in relating the virion polypeptides to N1 phage morphology. Electrophoretic analysis of empty heads revealed that the N1 phage head is composed of two major structural polypeptides (VP4 and VP6) and a single minor polypeptide (VP3). Analysis of ghosts with abnormally long tails indirectly demonstrated that VP5 is the major phage tail structural polypeptide. This conclusion was also indicated by a similar analysis of sonicated phage components that adsorb to host cells. Electrophoretic analysis of the ghosts also indicated that the minor polypeptide VP1 is a component of the N1 phage tail structure. VP2 may be an internal protein since it was not found in either empty heads or ghosts of the phage. A speculative model of the N1 virion was proposed on the basis of the location of the structural polypeptides, their molar ratios, and the similarity of N1 to lambda phage. Although inconclusive, the results of a preliminary investigation of intracellular, virus-specific protein synthesis during productive and abortive N1 infections of M. lysodeikticus strains 1 and 53-20 are also reported.



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Department Name

UNM Biology Department

First Committee Member (Chair)

Carl Ernest Cords, Jr.

Second Committee Member

Larry L. Barton

Third Committee Member

Roger James Radloff

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