Tail sheath protein of phage T4 constitutes the outer cylinder of the co-cylindrical structure of the tail, which appears to have evolved for efficient infection of the phage. It consists of 144 protomer molecules arranged in 24 annuli. Contraction of the sheath is exothermic and irreversible. Recently, primary structure of the protomer tail sheath protein (gp18) was determined from nucleotide sequence of the gene, which was subsequently confirmed by peptide analysis of the gene product. Use of the primary structure and available gene 18 mutants for further studying structure-function relation of the gene product and the mechanism of sheath contraction are discussed.
Phylogenetic conservation of a liverwort Marchantia polymorpha and tobacco Nicoliana tabacum chloroplast genomes has been elucidated by a comparative study of the complete nucleotide sequences. The genome encodes about 120 species of genes including those for proteins involved in photosynthesis and protein biogenesis and a complete set of rRNAs and tRNAs.
An outline of the evidence was given that the receptor molecules for two photorepellent sensory systems in Halobacterium halobium were the two rhodopsinlike proteins found recently in this extremely halophilic archaebacterium. One is a photointermediate of sensory rhodopsin. The name phoborhodopsin was proposed for the other.
X-ray equatorial diffraction experiments on lateral filament spacing of relaxed skinned muscle fibers were described. Two suggestions were made: Myosin heads contact to thinfilaments below 1, 0 lattice spacing of 35nm, and elastic elements between thick filaments in stretched fibers exert force which tends to pull thick filaments nearer together.
The photocontrol of polypeptide membrane conformation and functions was studied by using two membrane systems composed of poly (L-glutamic acid) with azobenzene groups and poly (L-glutamic acid) with pararosaniline groups, respectively. The photoresponsive behavior of these membranes can be explained in terms of the cooperative effect between photo-reaction of photochromic groups and the induced acid dissociation of L-glutamic acid groups in their membrane phase.
An approach to the study of the structure-function relation of ribonuclease T1 has been made by using genetic engineering techniques. Through the study of these artificial mutants, a new interaction at recognition site was eucidated and a new reaction mechanism of ribonuclease T1 was proposed.
To elucidate the mechanism of the high deformability of human erythrocytes, we have developed a new spin-labeling ESR method for measuring the deformability under shear flow. In this review, we introduce the principle of the method and its applications. Our results obtained so far by the new method are in excellent agreement with the typical results obtained by other method, i.e., rheoscopy or ectacytometery. In addition, the intercellular interactions during flow are also demonstrated to be measurable by the ESR method. The main advantages for the ESR method are 1. high sensitivity, 2. ability to measure at a high hematocrit (30-60%), and 3. ease of measuring cell deformability.