| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
|
|---|
| Research Abstract |
In order to elucidate the molecular mechanism of assembly and contraction of the tail sheath of bacteriophage T4, we have studieed the structure of the tail sheath protein, gp18. Gp18 has a molecular weight of 71,160 with 658 amino acid residues. 1)Nitration of tyrosine residues of gp18 by TNM (tetranitromethane) has revealed that 10 or 11 tyrosine residues (Tyr63/73, 254,270,455,460,493,523,535,569 and 590) out of 31 tyrosines were modifiable either in the monomeric state or the extended form of the tail sheath, but only five of these residues (Tyr254,270,455,460 and 493) were modified in the contracted form of the sheath. Especially, the nitration of Tyr270 and 455 proceeded independent of the association state of sp18. On the other hand, modification of Cys residues by a sulfhydryl group-specific reagent, ABD-F (4-aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole), has revealed that Cys377, Cys477 and Cys607, among 5 cysteine residues in gp18, have a sulfhydryl group. Cys402 and 406 are very likely connected by a disulfide bond.Cys607 can be modified n monomeric and associated states, whereas Cys477 is modifiable only in the monomeric state of gp18. 2) Limited proteolysis, immunoblotting and immuno-electron microscopy have shown that the trypsin-resistant fragment is Ala82-Lys316 and that, when combined with the data described above and below, the region of residues 250 through 410 appears to form the protruding part of the tail sheath as revealed by three-dimensional image reconstruction by Amos and Klug (1975). 3) Sequence determination of the tail sheath gene of Pseudomonas aeruginosa phage PS17 revealed that the tail sheath protein has 385 amino acids and that the corresponding sequence in T4 phage gp18 was split into two parts and present in two separate places in the primary structure.
|
