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Nine mutant forms of ribosomal proteins L1 from the bacterium Thermus thermophilus and the archaeon Methanococcus jannaschii were obtained. Their crystal structures were determined and analyzed. Earlier determined structure of S179C TthL1 was also thoroughly analyzed. Five from ten mutant proteins reveal essential changes of spatial structure caused by surface point mutation. It proves that for correct studies of biological processes by site-directed mutagenesis it is necessary to determine or at least to model spatial structures of mutant proteins. Detailed comparison of mutant L1 structures with that of corresponding wild type proteins reveals that side chain of a mutated amino acid residue tries to locate like the side chain of the original residue in the wild type protein. This observation helps to model the mutant structures.

Crystal structures of unbound protein L1 and of its complexes with ribosomal an messenger RNAs are analyzed. It is shown that the values of the apparent association rate constant for L1-RNA depend on conformation of unbound protein L1. It is suggested that L1 binds to rRNA with higher affinity than to mRNA because of additional interactions between domain II of L1 and the loop rRNA region, which is absent in mRNA.

Properties of specific interaction between ribosomal proteins and ribosomal RNAs were analyzed and a method for determination of "recognizing modules" on the protein surface was proposed. The method is based on the search of protein atoms making conserved H-bonds with RNA and forming an invariant spatial structure in homologous rRNA-protein complexes and in the isolated protein. A potential of the method is demonstrated on the determination of the recognizing modules on the surfaces of ribosomal proteins S8, S15 and L5.

In conjugation experiments of Escherichia coli K-12 Hfr strains and converted clones of Shigella flexneri var. y(-:3,4) that had acquired the capacity to synthesize type of antigens IV or V it is confirmed that the locus linked to lac-pro region in Sh. flexneri chromosome called Tp locus is a site of an attachment of prophages responsible for certain type specific antigens. Lac+ hybrids of the clone converted by phage IV lost the type specific antigen IV with the frequency comparable with the loss of the aforementioned antigen by wild strains of Sh. flexneri ser 4 in similar experiments carried out previously (90,8% and 97% respectively). Lac+ hybrids of the clones converted by phage V did not lose the type antigen that corresponded to the behaviour of wild strains of serotype 5b (V: 7,8) with double lysogenicity. It was shown that the clones converted by the aforementioned phage V had acquired an immunity not only to phage V, but to phage 7,8 as well. An independent segregation of immunity to phages V and 7,8 in lac+ hybrids of the converted clone was observed. It indicates that donor strain NTCC 595/52 carries two prophages, V and "defect" 7,8 (not expressing factor 7,8). A maintenance of antigen V observed in lac+ hybrids of the converted clone in this case confirms previous suggestions that an attachment of prophage 7,8 creates a state of some inhomology in this region disturbing the recombination process. The converting phage V isolated from the strain NTCC 595/52 is probably recombinant. An analysis of the hybrid classes allows to suggest the following approximate order of markers of the prophage on the chromosome of the converted clone: aV--imm V--imm 7,8--lac.

Homology of 18 amino acid sequences of lens gamma-crystallins of several vertebrates: frog, mouse, rat, calf and human being--has been considered. Pair sequence homology varies in the range from 57 to 100%, the mean value is equal to 74%. The spatial structures have been determined only for two calf gamma-crystallins. The protein molecule consists of four-fold repeated "motifs" (patterns) which are joint in two domains. After comparison of 18 gamma-crystallin sequences it was found that "motifs" domains and whole protein molecules have about 10, 30 and 58% conservative residues, respectively, that seem to be related to the evolution of these structural units. Structure analysis shows that almost all the conservative residues have an important structural meaning and play a basic role in the domain and molecular structure organization. This result allows us to make a conclusion about the homology of spatial structures of all considered gamma-crystallins of vertebrates.