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排序方式: 共有195条查询结果,搜索用时 31 毫秒
191.
Chloe A. Johnson Jake E. McGreig Sarah T. Jeanfavre Jonathan Walklate Carlos D. Vera Marta Farr Daniel P. Mulvihill Anthony J. Baines Martin Ridout Leslie A. Leinwand Mark N. Wass Michael A. Geeves 《PLoS biology》2021,19(6)
The speed of muscle contraction is related to body size; muscles in larger species contract at slower rates. Since contraction speed is a property of the myosin isoform expressed in a muscle, we investigated how sequence changes in a range of muscle myosin II isoforms enable this slower rate of muscle contraction. We considered 798 sequences from 13 mammalian myosin II isoforms to identify any adaptation to increasing body mass. We identified a correlation between body mass and sequence divergence for the motor domain of the 4 major adult myosin II isoforms (β/Type I, IIa, IIb, and IIx), suggesting that these isoforms have adapted to increasing body mass. In contrast, the non-muscle and developmental isoforms show no correlation of sequence divergence with body mass. Analysis of the motor domain sequence of β-myosin (predominant myosin in Type I/slow and cardiac muscle) from 67 mammals from 2 distinct clades identifies 16 sites, out of 800, associated with body mass (padj < 0.05) but not with the clade (padj > 0.05). Both clades change the same small set of amino acids, in the same order from small to large mammals, suggesting a limited number of ways in which contraction velocity can be successfully manipulated. To test this relationship, the 9 sites that differ between human and rat were mutated in the human β-myosin to match the rat sequence. Biochemical analysis revealed that the rat–human β-myosin chimera functioned like the native rat myosin with a 2-fold increase in both motility and in the rate of ADP release from the actin–myosin crossbridge (the step that limits contraction velocity). Thus, these sequence changes indicate adaptation of β-myosin as species mass increased to enable a reduced contraction velocity and heart rate.Heart and skeletal muscles of larger mammals contract more slowly than smaller ones. This study identifies amino acid changes in myosin isoforms that correlate with species size; mutating the residues in human β-myosin to match the rat sequence at these positions increased its in vitro velocity to that of the rat protein. 相似文献
192.
Molecular evolution of olfactomedin 总被引:2,自引:0,他引:2
Olfactomedin is a secreted polymeric glycoprotein of unknown function,
originally discovered at the mucociliary surface of the amphibian olfactory
neuroepithelium and subsequently found throughout the mammalian brain. As a
first step toward elucidating the function of olfactomedin, its
phylogenetic history was examined to identify conserved structural motifs.
Such conserved motifs may have functional significance and provide targets
for future mutagenesis studies aimed at establishing the function of this
protein. Previous studies revealed 33% amino acid sequence identity between
rat and frog olfactomedins in their carboxyl terminal segments. Further
analysis, however, reveals more extensive homologies throughout the
molecule. Despite significant sequence divergence, cysteines essential for
homopolymer formation such as the CXC motif near the amino terminus are
conserved, as is the characteristic glycosylation pattern, suggesting that
these posttranslational modifications are essential for function.
Furthermore, evolutionary analysis of a region of 53 amino acids of fish,
frog, rat, mouse, and human olfactomedins indicates that an ancestral
olfactomedin gene arose before the evolution of terrestrial vertebrates and
evolved independently in teleost, amphibian, and mammalian lineages.
Indeed, a distant olfactomedin homolog was identified in Caenorhabditis
elegans. Although the amino acid sequence of this invertebrate protein is
longer and highly divergent compared with its vertebrate homologs, the
protein from C. elegans shows remarkable similarities in terms of conserved
motifs and posttranslational modification sites. Six universally conserved
motifs were identified, and five of these are clustered in the carboxyl
terminal half of the protein. Sequence comparisons indicate that evolution
of the N-terminal half of the molecule involved extensive insertions and
deletions; the C-terminal segment evolved mostly through point mutations,
at least during vertebrate evolution. The widespread occurrence of
olfactomedin among vertebrates and invertebrates underscores the notion
that this protein has a function of universal importance. Furthermore,
extensive modification of its N-terminal half and the acquisition of a
C-terminal SDEL endoplasmic-reticulum- targeting sequence may have enabled
olfactomedin to adopt new functions in the mammalian central nervous
system.
相似文献
193.
194.
195.
The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus 总被引:1,自引:0,他引:1
Padgett RW; Loeb DD; Snyder LR; Edgell MH; Hutchison CA d 《Molecular biology and evolution》1987,4(1):30-45
Recombinant DNA clones have been isolated that contain 80 kb of the
beta-globin complex from the deer mouse, Peromyscus maniculatus.
Comparisons of this complex with that from the laboratory mouse, Mus
domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3,
Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin
complex since the two species diverged. Unlike other mammals studied thus
far, the deer mouse possesses three adult genes. Partial sequence analysis
indicates that each of the three adult genes is intact and hence may be
functional. Hybridization of one of the two Mus pseudogenes, Hbb-bh3, to
genomic blots from Peromyscus reveals that it has a homologous counterpart
in Peromyscus. Homologous genes to the two gamma-like Mus genes, Hbb-bhO
and Hbb-bhl, are also found in Peromyscus. The strong hybridization between
the Hbb-bhl genes and significant nucleotide similarity between the Hbb-bhO
genes suggest that both pairs are important for the ontogeny of these mice
although no known product has been identified for the Hbb-bhO genes. The
presence of Hbb-bhO and Hbb-bhl in Peromyscus suggests that the duplication
that created this related gene set occurred before the two lineages
diverged. A single gene for Hbb-y has been isolated from Peromyscus. The
adult region in Peromyscus has undergone significant divergence from the
same region in Mus, having three rather than two adult genes, the
acquisition of at least 15 kb of extra DNA relative to Mus, and possibly
the loss of the Hbb-bh2 pseudogene. The nonadult region of the complex, in
contrast, contains the same set of genes apparently distributed over the
same amount of DNA as in the Mus beta- globin complex. This observation
suggests that the embryonic region of the complex is more evolutionarily
stable than the adult region.
相似文献