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The early adaptive evolution of calmodulin 总被引:7,自引:0,他引:7
Baba ML; Goodman M; Berger-Cohn J; Demaille JG; Matsuda G 《Molecular biology and evolution》1984,1(6):442-455
Interaction between gene duplication and natural selection in molecular
evolution was investigated utilizing a phylogenetic tree constructed by the
parsimony procedure from amino acid sequences of 50 calmodulin- family
protein members. The 50 sequences, belonging to seven protein lineages
related by gene duplication (calmodulin itself, troponin-C, alkali and
regulatory light chains of myosin, parvalbumin, intestinal calcium-binding
protein, and glial S-100 phenylalanine-rich protein), came from a wide
range of eukaryotic taxa and yielded a denser tree (more branch points
within each lineage) than in earlier studies. Evidence obtained from the
reconstructed pattern of base substitutions and deletions in these
ancestral loci suggests that, during the early history of the family,
selection acted as a transforming force on expressed genes among the
duplicates to encode molecular sites with new or modified functions. In
later stages of descent, however, selection was a conserving force that
preserved the structures of many coadapted functional sites. Each branch of
the family was found to have a unique average tempo of evolutionary change,
apparently regulated through functional constraints. Proteins whose
functions dictate multiple interaction with several other macromolecules
evolved more slowly than those which display fewer protein-protein and
protein-ion interactions, e.g., calmodulin and next troponin-C evolved at
the slowest average rates, whereas parvalbumin evolved at the fastest. The
history of all lineages, however, appears to be characterized by rapid
rates of evolutionary change in earlier periods, followed by slower rates
in more recent periods. A particularly sharp contrast between such fast and
slow rates is found in the evolution of calmodulin, whose rate of change in
earlier eukaryotes was manyfold faster than the average rate over the past
1 billion years. In fact, the amino acid replacements in the nascent
calmodulin lineage occurred at residue positions that in extant metazoans
are largely invariable, lending further support to the Darwinian hypothesis
that natural selection is both a creative and a conserving force in
molecular evolution.
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Proteolytic enzymes have been used both to modify properties of the cell membrane and to dissociate cells from many tissues including pituitary (4, 5, 12). Exposure of secretory tissues to pronase can alter their secretory response. Thus incubation of pancreatic islets of Langerhans in the presence of low concentrations of pronase increased the subsequent release of insulin in the presence of stimulatory and nonstimulatory glucose concentrations (7). The purpose of the present investigation was to determine whether low concentrations of pronase have the same stimulatory effect on the release of a pituitary hormone, growth hormone. Such an effect on hormone release could be of some importance in view of the development of dissociated cell systems as models for the study of the control of hormone release (4, 5). 相似文献
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J G Spenney G Saccomani H L Spitzer M Tomana G Sachs 《Archives of biochemistry and biophysics》1974,161(2):456-471
Lipid, carbohydrate, amino acid, and polypeptide composition of 2 fractions of cell membranes obtained by sucrose-Ficoll zonal density gradient fractionation of gastric mucosal homogenates has been studied. The membranes with density = 1.04 contain 0.7 μmole lipid P and 0.54 μmole cholesterol/mg protein, while the membranes of density 1.10 contain only 0.25 μmole lipid P and 0.28 μmole cholesterol/mg protein. Phosphatidylcholine and phosphatidylethanolamine are the most abundant phospholipids. Free fatty acids were present. Carbohydrates were most abundant in the proteins of the Peak II membranes (density = 1.10). One polypeptide band was dominant on sodium dodecyl sulfate, Triton X-100, and Brij 36T gels, and the adenosine triphosphatase activity in Brij 36T gels was found to have a relative mobility of 0.14 and 0.19 in the two fractions. 相似文献
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