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71.
Conservation of alternative splicing and genomic organization of the myosin alkali light-chain (Mlc1) gene among Drosophila species 总被引:3,自引:0,他引:3
The Mlc1 gene of Drosophila melanogaster encodes two MLC1 isoforms via
developmentally regulated alternative pre-mRNA splicing. In larval muscle
and tubular and abdominal muscles of adults, all of the six exons are
included in the spliced mRNA, whereas, in the fibrillar indirect flight
muscle of adult, exon 5 is excluded from the mRNA. We show that this
tissue-specific pattern of alternative splicing of the Mlc1 pre-mRNA is
conserved in D. simulans, D. pseudoobscura, and D. virilis. Isolation and
sequencing of the Mlc1 genes from these three other Drosophila species have
revealed that the overall organization of the genes is identical and that
the genes have maintained a very high level of sequence identity within the
coding region. Pairwise amino acid identities are 94%-99%, and there are no
charge changes among the proteins. Total nucleotide divergence within the
coding region of the four genes supports the accepted genealogy of these
species, but the data indicate a significantly higher rate of amino acid
replacement in the branch leading to D. pseudoobscura. A comparison of
nucleotide substitutions in the coding portions of exon 5 and exon 6, which
encode the alternative carboxyl termini of the two MLC1 isoforms, suggests
that exon 5 is subject to greater evolutionary constraints than is exon 6.
In addition to the coding sequences, there is significant sequence
conservation within the 5' and 3' noncoding DNA and two of the introns,
including one that flanks exon 5. These regions are candidates for cis-
regulatory elements. Our results suggest that evolutionary constraints are
acting on both the coding and noncoding sequences of the Mlc1 gene to
maintain proper expression and function of the two MLC1 polypeptides.
相似文献
72.
73.
Weissman SJ Chattopadhyay S Aprikian P Obata-Yasuoka M Yarova-Yarovaya Y Stapleton A Ba-Thein W Dykhuizen D Johnson JR Sokurenko EV 《Molecular microbiology》2006,59(3):975-988
Type 1 fimbriae of Escherichia coli mediate mannose-specific adhesion to host epithelial surfaces and consist of a major, antigenically variable pilin subunit, FimA, and a minor, structurally conserved adhesive subunit, FimH, located on the fimbrial tip. We have analysed the variability of fimA and fimH in strains of vaginal and other origin that belong to one of the most prominent clonal groups of extraintestinal pathogenic E. coli, comprised of O1:K1-, O2:K1- and O18:K1-based serotypes. Multiple locus sequence typing (MLST) of this group revealed that the strains have identical (at all but one nucleotide position) eight housekeeping loci around the genome and belong to the ST95 complex defined by the publicly available E. coli MLST database. Multiple highly diverse fimA alleles have been introduced into the ST95 clonal complex via horizontal transfer, at a frequency comparable to that of genes defining the major O- and H-antigens. However, no further significant FimA diversification has occurred via point mutation after the transfers. In contrast, while fimH alleles also move horizontally (along with the fimA loci), they acquire point amino acid replacements at a higher rate than either housekeeping genes or fimA. These FimH mutations enhance binding to monomannose receptors and bacterial tropism for human vaginal epithelium. A similar pattern of rapid within-clonal structural evolution of the adhesive, but not pilin, subunit is also seen, respectively, in papG and papA alleles of the di-galactose-specific P-fimbriae. Thus, while structurally diverse pilin subunits of E. coli fimbriae are under selective pressure for frequent horizontal transfer between clones, the adhesive subunits of extraintestinal E. coli are under strong positive selection (Dn/Ds > 1 for fimH and papG) for functionally adaptive amino acid replacements. 相似文献
74.
IL-7 is known foremost for its immunostimulatory capacities, including potent T cell-dependent catabolic effects on bone. In joint diseases like rheumatoid arthritis and osteoarthritis, IL-7, via immune activation, can induce joint destruction. Now it has been demonstrated that increased IL-7 levels are produced by human articular chondrocytes of older individuals and osteoarthritis patients. IL-7 stimulates production of proteases by IL-7 receptor-expressing chondrocytes and enhances cartilage matrix degradation. This indicates that IL-7, indirectly via immune activation, but also by a direct action on cartilage, contributes to joint destruction in rheumatic diseases. 相似文献
75.
FimH forms catch bonds that are enhanced by mechanical force due to allosteric regulation 总被引:1,自引:0,他引:1
Yakovenko O Sharma S Forero M Tchesnokova V Aprikian P Kidd B Mach A Vogel V Sokurenko E Thomas WE 《The Journal of biological chemistry》2008,283(17):11596-11605
The bacterial adhesive protein, FimH, is the most common adhesin of Escherichia coli and mediates weak adhesion at low flow but strong adhesion at high flow. There is evidence that this occurs because FimH forms catch bonds, defined as bonds that are strengthened by tensile mechanical force. Here, we applied force to single isolated FimH bonds with an atomic force microscope in order to test this directly. If force was loaded slowly, most of the bonds broke up at low force (<60 piconewtons of rupture force). However, when force was loaded rapidly, all bonds survived until much higher force (140-180 piconewtons of rupture force), behavior that indicates a catch bond. Structural mutations or pretreatment with a monoclonal antibody, both of which allosterically stabilize a high affinity conformation of FimH, cause all bonds to survive until high forces regardless of the rate at which force is applied. Pretreatment of FimH bonds with intermediate force has the same strengthening effect on the bonds. This demonstrates that FimH forms catch bonds and that tensile force induces an allosteric switch to the high affinity, strong binding conformation of the adhesin. The catch bond behavior of FimH, the amount of force needed to regulate FimH, and the allosteric mechanism all provide insight into how bacteria bind and form biofilms in fluid flow. Additionally, these observations may provide a means for designing antiadhesive mechanisms. 相似文献
76.
Adelmo L Cechin Marialva Sinigaglia Ney Lemke Sérgio Echeverrigaray Odalys G Cabrera Gonçalo AG Pereira José CM Mombach 《BMC plant biology》2008,8(1):50
Background
NEP1-like proteins (NLPs) are a novel family of microbial elicitors of plant necrosis. Some NLPs induce a hypersensitive-like response in dicot plants though the basis for this response remains unclear. In addition, the spatial structure and the role of these highly conserved proteins are not known. 相似文献77.
R V Petrov V S Aprikian Iu O Sergeev S I Elkina V V Sergeev 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1988,(5):62-64
The protective properties of myelopeptides in the development of bacterial infection in mice and young pigs, caused by S. typhimurium 415, S. cholerae-suis 1422 and 370, have been studied. Myelopeptides have been found to possess protective properties when injected into animals infected with S. typhimurium and S. cholerae-suis in lethal doses. The best protective effect (survival rate of 100%) has been achieved by the injection of myelopeptides 24 hours before challenge. Myelopeptides have also been found to promote the weight gain of young pigs infected with S. cholerae-suis. 相似文献
78.
79.
80.
V S Aprikian A A Mikha?lova R V Petrov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1992,(9-10):71-74
Penicillin, streptomycin and gentamicin, when introduced into mice in a single injection in doses of 0.5-500,000 U/kg, produced different changes in the phagocytic activity of mouse peritoneal macrophages. Bactericidal doses of these antibiotics either suppressed the activity of macrophages or left it unchanged. Their sub-bactericidal doses enhanced the phagocytic activity of macrophages. Combined use of penicillin and streptomycin produced a synergic effect. 相似文献