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Sequence of a full-length cDNA for rat lung beta-galactoside-binding protein: primary and secondary structure of the lectin 总被引:5,自引:0,他引:5
A full-length cDNA for rat lung beta-galactoside lectin (subunit Mr approximately 14,000, lectin 14K) was cloned and the nucleotide sequence determined. The deduced amino acid sequence agrees with the amino acid composition and direct amino acid sequence analysis of purified rat lung lectin peptides. We found that the amino-terminal alanine is blocked with an acetyl group. Comparison of the amino acid sequence with other proteins shows a high degree of homology only with other vertebrate lectin sequences, supporting the suggestion that these lectins may constitute a unique class of vertebrate proteins. The amino acid composition and sequence of lectin peptides, the sequence of lectin cDNA, and isoelectric focusing of purified lectin indicate that rat lung lectin 14K is composed predominantly of a single protein. In addition, rat uterus lectin 14K was found to be the same protein as that present in lung. We characterized the secondary and tertiary structure of rat lung lectin 14K by circular dichroism, by analytical ultracentrifugation, and by computer analysis of its primary structure. Results of these experiments suggest that lectin 14K is primarily a hydrophilic protein with an asymmetric, elongated structure consisting of approximately equal amounts of alpha helix, beta sheet, beta turn, and random coil. We found that Cys-2 and Cys-130 react most rapidly with iodoacetamide; one or both of these residues may be primarily responsible for the thiol requirement of lectin activity. 相似文献
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Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
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大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献
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D Liebowitz G D Massaro D Massaro 《Journal of applied physiology (Bethesda, Md. : 1985)》1984,56(3):564-567
We examined the effect of adrenalectomy (ADX) on aspects of the surfactant system of adult rats. Five days after bilateral ADX, ADX rats had about 20% less disaturated phosphatidylcholine (DSPC) in lung lavage returns (airway DSPC) than sham-operated rats, but the amount of tissue DSPC was not different between the groups; airway DSPC formed 12.8 +/- 0.5% of total DSPC (airway + tissue) in ADX and 15.9 +/- 0.7% in sham-ADX rats. An ultrastructural morphometric analysis of alveolar type 2 cells did not reveal an effect of ADX on lamellar body volume density or surface-to-volume ratio. ADX rats had heavier lungs (not as a result of edema) than sham-ADX rats. Treatment of ADX rats with hydrocortisone returned the amount of DSPC toward normal and eliminated the increase of lung weight. ADX did not alter the recoil of saline-filled lungs but did slightly increase the recoil of air-filled lungs. We conclude that corticosteroid hormones influence the in vivo functioning of the surfactant system of adult rats, but this effect seems to be slight. 相似文献
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Postnatal development of the bronchiolar Clara cell in rats 总被引:1,自引:0,他引:1