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91.
Determinants of the quantity of the stable SecY complex in the Escherichia coli cell. 总被引:11,自引:3,他引:8
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While SecY in wild-type Escherichia coli cells is stable and is complexed with other proteins within the membrane, moderately overexpressed and presumably uncomplexed SecY was degraded with a half-life of 2 min. The fact that the amount of stable SecY is strictly regulated by the degradation of excess SecY was demonstrated by competitive entry of the SecY+ protein and a SecY-LacZ alpha fusion protein into the stable pool. Simultaneous overexpression of SecE led to complete stabilization of excess SecY. Overproduced SecD and SecF did not affect the stability of SecY, but plasmids carrying ORF12 located within the secD-secF operon partially stabilized this protein. In contrast, mutational reduction of the SecE content (but not the ORF12 content) led to the appearance of two populations of newly synthesized SecY molecules, one that was immediately degraded and one that was completely stable. Thus, the E. coli cell is equipped with a system that eliminates SecY unless it is complexed with SecE, a limiting partner of SecY. Our observations implied that in wild-type cells, SecY and SecE rapidly associate with each other and remain complexed. 相似文献
92.
Summary The evolutionary relation of vertebrate myoglobin and the hemoglobin chains including the agnathan hemoglobin chain is investigated on the basis of a new view of amino acid changes that is developed by canonical discriminant analysis of amino acid residues at individual sites. In contrast to the clear discrimination of amino acid residues between myoglobin, hemoglobin a chain, and hemoglobin chain in warm-blood vertebrates, the three types of globins in the lower class of vertebrates show so much variation that they are not well discriminated. This is seen particularly at the sites that are ascertained in mammals to carry the amino acid residues participating in stabilizing the monomeric structure in myoglobin and the residues forming the subunit contacts in hemoglobin. At these sites, agnathan hemoglobin chains are evaluated to be intermediate between the myoglobin and hemoglobin chains of gnathostomes. The variation in the phylogenetically lower class of globins is also seen in the internal region; there the amino acid residues of myoglobin and hemoglobin chains in the phylogenetically higher class exhibit an example of parallel evolution at the molecular level. New quantities, the distance of sequence property between discriminated groups and the variation within each group, are derived from the values of discriminant functions along the peptide chain, and this set of quantities simply describes an overall feature of globins such that the distinction between the three types of globins has been clearer as the vertebrates have evolved to become jawed, landed, and warm-blooded. This result strongly suggests that the functional constraint on the amino acid sequence of a protein is changed by living conditions and that severe conditions constitute a driving force that creates a distinctive protein from a less-constrained protein.Offprint requests to: J. Otsuka 相似文献
93.
Kenji Kawanaka 《Primates; journal of primatology》1993,34(3):255-270
Proximity partner choice by male chimpanzees of various age classes was analyzed in relation to their spatial positioning.
Field work was carried out twice at the Mahale Mountains National Park, Tanzania. Proximity data were recorded at 3 and 10m
from the focal animal. The data for the proximity between the focal male and other individuals allowed the males to be classified
into two categories according to both criteria: early adolescence to young adult, and prime to old age. Between the males,
the 3m proximity data permitted a classification into two categories as above, but those for 10m did not. These two spatial
distances thus probably have different meanings for the males. The numbers of male proximity partners and proximity with the
alpha male also allowed the males to be classified into two categories: early and late adolescence, and young adult to old
age. Together, the above results support the classification of males into three age-graded categories: (1) early and late
adolescence, (2) young adult, and (3) prime to old age. This does not arise because the males of each category form an age
group. Prime or older males are most frequently in proximity, while their juniors consistently attempt to approach them. However,
even prime or older males are not equally in proximity with one another. Their proximity partners change as time passes. Probably
recognizing such changes, they form coalitions or are in rivalry. The sexual interest of adolescent males is probably a factor
stimulating them to separate from their mothers, and to approach older males. Young adult males, even though physically mature,
do not have equal proximity relations with older males. They are not yet sufficiently qualified to join the coalitions formed
by their seniors. 相似文献
94.
Nobuakira Takeda Akira Tanamura Takaaki Iwai Mitsutoshi Kato Kenji Noma Makoto Nagano 《Molecular and cellular biochemistry》1993,129(2):139-143
The effects of captopril, an angiotensin-converting enzyme inhibitor, on congestive heart failure (CHF) were investigated in animal and clinical studies. Congestive heart failure was induced in rats by a combination of pressure and volume overload. Cardiac pressure overload was induced by constricting one renal artery (Goldblatt rat) and volume overload was induced by aorto-caval fistula. Captopril (100 mg/kg/day) was then administered for 14 weeks. Isometric contraction was assessed using isolated left ventricular papillary muscles. The maximum developed tension and the maximum rate of increase in tension (dT/dtmax) were decreased in untreated rats with CHF and improved in captopriltreated rats. The left ventricular myosin isoenzyme pattern was shifted towards V3 in untreated rats with CHF, and was shifted back towards V1 in the captopril-treated rats. In the clinical study, captopril (37.5–75 mg/day) was administered to patients with cardiomyopathy for 12 months. There was no effect on left ventricular mass in hypertrophic cardiomyopathy, although systolic anterior motion of the mitral valve disappeared in one patient. In dilated cardiomyopathy, however, left ventricular mass tended to decrease. These results indicate that captopril has a beneficial effect in congestive heart failure. 相似文献
95.
96.
Yukie Takahashi Masako Sohnaka Minoru Nakao Kenji Miyamoto Masahito Fukunaga 《Microbiology and immunology》1993,37(9):721-727
Thirty-two Borrelia isolates were obtained from the adult stage of ixodid ticks, Ixodes ovatus, collected in various localities in Japan. Borrelial isolates were cultivated and analyzed by polyacrylamide gel electrophoresis, with monoclonal antibodies, by pulsed field gel electrophoresis, and by genomic Southern hybridization. All borrelial isolates showed similar protein profiles and monoclonal antibody reactivities, while plasmid profiles were rather diverse. Genomic hybridization using rRNA gene probes demonstrated the genetic similarities of those isolates. We found no significant differences among the borrelial isolates tested, and the restriction fragment length polymorphism patterns of I. ovatus isolates were quite distinct from those of borrelial strains associated with Lyme disease. Therefore, the isolates of Borrelia obtained from I. ovatus were thought to fall into different genospecies. 相似文献
97.
Kenji Matsuura Hideo Takashina 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1993,616(2)
A gas chromatographic—mass spectrometric method for determining tiopronin, which has a thiol group, in human blood has been described. To prevent the oxidative degradation of tiopronin in the blood, its thiol group was immediately protected by treatment with isobutyl acrylate, which reacted readily with tiopronin in a 0.1 M Na2HPO4 solution (pH 9.1). The reaction was quantitative within 30 min. The blood sample was deproteinized and purified by a combination of liquid—liquid extraction and solid-phase extraction. Finally, the carboxyl moiety of the ester adduct was derivatized to the pentafluorobenzyl ester. The derivatives of tiopronin and the internal standard were analysed with gas chromatography—mass spectrometry. The precision of the method was satisfactory, and the calibration curve had good linearity in the concentration range investigated. The limit of determination of tiopronin in blood was estimated to be ca. 1 ng/ml. 相似文献
98.
99.
Dispersal propensity of green leafhoppers was compared between a tropical species, Nephotettix virescens, and a temperate species, N. cincticeps. The flight ability was measured with tethered flight technique under laboratory conditions (25°C, 16L-8D). The pre-flight period was shorter and the flight duration was longer in N. virescens than in N. cincticeps in both sexes. No significant correlations were found between the flight activity and morphometric characters for either of the two species. The results suggested that dispersal propensity of N. virescens is higher than that of N. cincticeps. 相似文献
100.
β-Galactosidase (β-Galase, EC 3.2.1.23) activity has been detected in a culture medium of cell suspension cultures of carrot ( Daucus carota L. cv. Kintoki). The extracellular β-Galase (β-Galase-II) was purified to electrophoretic homogeneity from the concentrated medium using ammonium sulfate precipitation, chromatography on CM-Sephadex C-50. DEAE-Sepharose CL-6B and Sephacryl S-200HR, and preparative PAGE. The molecular mass of the purified enzyme was estimated to be 65 kDa by Sephacryl S-200HR gel-permeation, and 60 kDa by SDS-PAGE after treatment with SDS and 2-mercaptoethanol. The pI was 6.5. The Km and Vmax values for p -nitrophenyl (PNP)-β-D-galactopyranoside were 0.17 m M and 31.9 μmol (mg protein)-1 , h-1 , respectively. The optimal activity in McIlvaine's buffer occurred at pH 4.0–4.4. The enzyme activity was inhibited by Co24 , Cu2+ , Hg2- , p -chloromercuribenzoate (PCMB) and D-galactono-1,4-lactone. The enzyme acted on citrus galactan and larchwood arabinogalactan in an exo-fashion, and was slightly involved in the hydrolysis of an acidic pectic polymer containing arabinosyl and galactosyl residues and in the breakdown of cell walls isolated from carrot cell cultures. 相似文献