The Structure of Physarum polycephalum hemagglutinin I suggests a minimal carbohydrate recognition domain of legume lectin fold

Physarum polycephalum hemagglutinin I (HA1) is a 104-residue protein that is secreted to extracellular space. The crystal structure of HA1 has a β-sandwich fold found among lectin structures, such as legume lectins and galectins. Interestingly, the β-sandwich of HA1 lacks a jelly roll motif and is essentially composed of two simple up-and-down β-sheets. This up-and-down β-sheet motif is well conserved in other legume lectin-like proteins derived from animals, plants, bacteria, and viruses. It is more noteworthy that the up-and-down β-sheet motif includes many residues that make contact with the target carbohydrates. Our NMR data demonstrate that HA1 lacking a jelly roll motif also binds to its target glycopeptide. Taken together, these data show that the up-and-down β-sheet motif provides a fundamental scaffold for the binding of legume lectin-like proteins to the target carbohydrates, and the structure of HA1 suggests a minimal carbohydrate recognition domain.     

Interactions between viomycin resistance and streptomycin resistance on ribosomes of Mycobacterium smegmatis.

We have investigated the mechanism of the expression of resistance to high levels of viomycin and coresistance to streptomycin in a mutant strain of Mycobacterium smegmatis ATCC 14468 (AC-13) which was obtained by serial transfers of parental cells to media containing increasing concentrations of viomycin. It was shown previously that resistance to viomycin by strain AC-13 was due to an alteration in the 50 S ribosomal subunit (20). However, genetic analysis has shown that mutation in 50 S subunits alone gave only low level resistance to viomycin. When a streptomycin resistant mutation (caused by an alteration in the 30 S subunit) was introduced into the low level viomycin resistant recombinant strains, most of them were highly resistant to viomycin. Some recombinants were resistant to intermediate levels of viomycin, and the remainder were not affected by the introduction of the str^r allele. Studies with in vitro cell-free systems have shown that streptomycin resistant 30 S ribosomal subunits obtained from a high level viomycin resistant recombinant were able to modify the levels of resistance to viomycin expressed by the 50 S ribosomal subunit. These findings provide additional evidence concerning the functional relationship between 30 S and 50 S ribosomal components in ribosomes.     

Genetic and biochemical analysis of ribosomal proteins of minocycline-susceptible and -resistant Mycobacterium smegmatis.

A minocycline (MINO)-resistant mutant was isolated from Mycobacterium smegmatis strain Rabinowitschi. Polypeptide synthesis in the cell-free system prepared from the mutant was resistant to minocycline (MINO) because of alterated 30S ribosomal subunits. Upon two-dimensional gel electrophoresis, two proteins of 30S subunit were found to be altered. MINO resistance phenotype was transferred by mating to the recipient strain P-53. MINO resistance phenotype of a recombinant thus obtained was transferred by a different mating system to the recipient strain Jucho, once again. Ribosomal proteins of each of the donors, recipients and recombinants were analyzed and compared on 2-dimensional (2D) electrophoresis. Approximately 50 ribosomal proteins were observed in 70S ribosomes. Some proteins were differently electrophoresed in different strains. The 30S ribosomal subunits contained at least 19 proteins and 50S ribosomal subunits contained at least 23 proteins. Some proteins were easily washed off during dissociation of subunits in sucrose gradients. At least one protein (designated F) in both subunits was observed at the same position. One protein designated C in 30S subunits could be co-transferred to the recipient cells together with resistance phenotype at the frequency of 100% in the 30 recombinants examined so far. The other protein designated D in 30S subunits could be transferred at the frequency of 86-88%. Three other proteins in 50S subunits could be co-transferred to the recipient strain at a lower frequency. Minocycline resistance, therefore, could be mapped close to genes encoding the structure of ribosomal proteins in M. smegmatis.     

Interaction between 30 S ribosomal components in a viomycin resistant mutant of Mycobacterium smegmatis.

A high level viomycin resistant mutant of Mycobacterium smegmatis ATCC 14468 (AC16) was analyzed genetically and biochemically in an attempt to understand the mechanisms of expression of high level viomycin resistance and co-resistance to kanamycin and streptomycin. Genetic analysis has shown that at least three different genes (vicC, str, and kan) were involved in the phenotypic expression of drug resistance in AC16, and high level resistance to viomycin was due to interactions between the products of these genes.     

Antibiotic susceptibility of Legionella pneumophia Philadelphia-1 in cultured guinea-pig peritoneal macrophages

The effect of antimicrobial agents on the intracellular multiplication of Legionella pneumophila in cultured guinea-pig peritoneal macrophages was measured. Beta-lactam antibiotics at concentrations 5 to 400 times the MIC in vitro did not inhibit the intracellular growth of the organism. Gentamicin inhibited the growth considerably but failed to eliminate the organism from the phagocytic mixture. Chloramphenicol or tetracycline at 10 micrograms ml-1 (40 or 5 times the MIC in vitro respectively) did not eliminate the organism. At a higher concentration (30 micrograms ml-1), however, these drugs eliminated the bacterium from the mixture. Only erythromycin and rifampin were effective in killing the organism at very low concentration (1 microgram ml-1). Intracellular multiplication of L. pneumophila was observed clearly by light microscopy using Wright-Giemsa staining.     

Underwater vocalizations and associated behavior in captive ringed seals (<Emphasis Type="Italic">Pusa hispida</Emphasis>)

In pinniped species, especially those that mate in the water, acoustic communication is suggested to play an important role in various aspects of behavior. However, little is known about the behavioral context or function of vocalization, principally because direct observation is difficult in the wild. In the present study, we analyzed the seasonality, sexual differences, and behavioral contexts of the vocalizations of captive ringed seals to explore the function of such communication. The behavior of and underwater sounds made by three ringed seals (an adult male, an adult female, and a subadult female) living in Otaru Aquarium, Japan, were recorded for 19 days between August 2011 and April 2012. Six call types (long snort, knock, yelp, bark, click, and woof) were identified in the recordings. The 12 observed social behaviors could be categorized into three categories (male courtship, aggression, and submission). All call types except clicks were vocalized during social behavior. Vocalizations of all types increased during the breeding season. The long snorts were only produced by the adult male toward an adult female during his courtship behavior. All three individuals emitted knocks, yelps, and bark sounds. Of these three call types, knocks were associated with aggressive behavior or the male’s courtship behavior. In contrast, alternate series of yelps and barks were vocalized by the recipients of aggressive behaviors, suggesting their function as submissive signals. This study could be applied to the monitoring of wild ringed seals with passive acoustic recordings to assess not only their distribution but also their behavior.     

Membrane IgM, IgD, and IgG act as signal transmission molecules in a series of B lymphomas

Increases in intracellular free calcium concentration ((Ca2+)i) were observed in response to anti-immunoglobulin (Ig) antibodies in each of six B cell tumors or B cell hybridomas bearing mu or delta chains on their cell surface. The BAL17 cell line, bearing mu and delta chains on its surface, behaved similarly to mature B cells in the following respects. Anti-IgM and anti-IgD antibodies caused increases in (Ca2+)i and inositol phospholipid metabolism; the initial increases in (Ca2+)i were derived partly from an intracellular Ca2+ pool; lipopolysaccharide, phorbol myristate acetate (PMA), B cell stimulatory factor-1, and antibodies to class I and class II major histocompatibility molecules and to the Fc gamma receptor failed to cause increases in (Ca2+)i or in inositol phospholipid metabolism; and increases in (Ca2+)i and inositol phospholipid metabolism in response to anti-Ig were inhibited by pretreatment with PMA. Furthermore A20, an IgG2a bearing lymphoma, showed increases in (Ca2+)i in response to anti-IgG2a, and a lymphoma cell line (6G8-2E10) expressing membrane IgG2b as a result of DNA-mediated transfer of the gamma 2b H chain gene, showed increases in (Ca2+)i in response to anti-IgG2b. These results indicate that Ig-bearing lymphomas display early events in B cell activation after receptor cross-linkage and can be used for detailed studies of the activation process.     

Paraquat Resistant Tobacco Calluses with Enhanced Superoxide Dismutase Activity

Seven paraquat resistant calluses of tobacco (Nicotiana tabacumL. cv. Samsun) were obtained by three successive screeningsof protoplast-derived calluses on a paraquat containing medium.Superoxide dismutase (SOD) activity of the resistant calluseswas 14- to 159-fold that of the leaf cells on protein basis.Paraquat-resistant calluses, however, showed little increasein catalase and peroxidase activities. More than 90% of SODactivity in the resistant calluses was inhibited by KCN, aswas the SOD activity in leaves, indicating that the major SODin the callus appears to be the Cu, Zn containing enzyme. Thecallus cells, however, expressed the immunologically distinguishedSOD isozyme from the enzyme in the leaves. (Received April 23, 1984; Accepted August 6, 1984)     

Mechanism of antibiotic resistance in Mycobacterium intracellulare

The mechanism of resistance of Mycobacterium intracellulare strain 103 and other clinical isolates to a variety of drugs including aminoglycoside and peptide antibiotics was investigated. Enzymatic inactivation of aminoglycoside and peptide antibiotics could not be demonstrated. Ribosomes of the strain were found to be sensitive to the antibiotics. The levels of resistance of strain 103 and other clinical isolates decreased dramatically when the culture medium was changed from Dubos agar to Tween 80-containing agar. These results suggest that a permeability barrier is the reason for naturally occurring resistance in M. intracellulare.