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151.
José Carreira José Manuel Andreu Manuel Nieto Emilio Muñoz 《Molecular and cellular biochemistry》1976,10(2):67-76
Summary Two new forms of the plasma membrane ATP-ase ofMicrococcus lysodeikticus NCTC 2665 were isolated from a sub-strain of the microorganism by polyacrylamide gel electrophoresis. One of them had a mol.wt of 368,000 and a very low specific activity (0.80 µ mol.min–1.mg protein–1) that could not be stimulated by trypsin. This form has been called BI (strain B, inactive). If the electrophoresis was carried out in the presence of reducing agents (i.e., dithiothreitol) and the pH of the effluent maintained at a value of 8.5 another form of the enzyme was obtained. This had a mol.wt of 385,000 and a specific activity of 2.5–5.0 µ mol.min–1.mg protein–1 that could be stimulated by trypsin to 5–10 µ mol.min–1.mg protein–1. This preparation of the ATPase has been called form BA (strain B, enzyme active). The subunit composition of both forms has been studied by sodium dodecyl sulphate and urea gel electrophoresis and compared to that of the enzyme previously purified from the original strain (form A). The three forms of the enzyme had similar and subunits, with mol.wt of about 50,000 and 30,000 dalton, respectively. They also had in common the component(s) of relative mobility 1.0, whose status as true subunit(s) of the enzyme remains yet to be established. However, subunit, that had a mol.wt of about a 52,500 in form A (Andreu
et al. Eur. J. Biochem. (1973) 37, 505–515), had a mol.wt similar to in form BI and about 60,000 in form BA. Furthermore BA usually showed two types of this subunit ( and) and an additional peptide chain () with a mol.wt of about 25,000 dalton. This latter subunit seemed to account for the stimulation by trypsin of form BA.Forms BA could be converted to BI by storage and freezing and thawing. Conventional protease activity could not be detected in any of the purified ATPase forms and addition of protease inhibitors to form BA failed to prevent its conversion to form BI. The low activity form (BI) was more stable than the active forms of the enzyme and also differed in its circular dichroism. These results show thatM. lysodeikticus ATPase can be isolated in several forms. Although these variations may be artifacts caused by the purification procedures, they provide model systems for understanding the structural and functional relationships of the enzyme and for drawing some speculations about its functionin vivo. 相似文献
152.
153.
A preparation of ATPase from the membranes of Micrococcus lysodeikticus, solubilized and more than 95 %. pure, showed two main bands in analytical polyacrylamide gel electrophoresis. They did not correspond to isoenzymes because one band could be converted into the other by exposure to a mildly alkaline pH value. The conversion was paralleled by changes in molecular weight, circular dichroism and catalytic properties. Denaturation by pH at 25 °C was followed by means of circular dichroism, ultracentrifugation and polyacrylamide gel electrophoresis. A large conformational transition took place in the acid range with midpoints at about pH = 3.6 (I = 10?4 M), 4.3 (I = 0.03 M) and 5.3 (I = 0.1 M). The transition was irreversible. Strong aggregation of the protein occurred in this range of pH. The final product was largely random coil, but even at pH 1.5 dissociation into individual subunits was not complete. However, partial dissociation took place at pH 5 (I = 0.028 M). At this pH value the enzyme was inactive, but 20–30 % of the activity could be recovered when the pH was returned to 7.5.In the alkaline region the midpoint of the transition occurred near pH = 11 (I = 0.028 M). The pK of most of the tyrosine residues of the protein was about 10.9. The unfolding was irreversible and the protein was soon converted into peptide species with molecular weights lower than those determined for the subunits by gel clectrophoresis in the presence of sodium dodecyl sulphate. Conventional proteolysis did not account for the transformation. 相似文献
154.
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157.
Identification of a novel adhesion molecule in human leukocytes by monoclonal antibody LB-2 总被引:6,自引:0,他引:6
Manuel Patarroyo Edward A. Clark Jacqueline Prieto Carmela Kantor Carl G. Gahmberg 《FEBS letters》1987,210(2):127-131
Monoclonal antibody LB-2 to a surface antigen on human B cells, lymphoblast, monocytes and vascular endothelial cells largely inhibited adhesion among Epstein Barr virus-immortalized normal B cells (EBV-B) and concanavalin A-stimulated blood mononuclear cells (Con A-BMC) before and after phorbol ester treatment. The antibody inhibited to a lesser extent phorbol ester-induced aggregation of monocytes, U937 cells and fresh BMC and had virtually no inhibitory effect on the adhesion among enriched T cells and granulocytes. A surface glycoprotein band of 84 kDa was obtained from EBV-B cells by immunoprecipitation and gel electrophoresis. Immunological and biochemical studies clearly distinguished this molecule from gp90 and associated glycoproteins which also mediate leukocyte adhesion. 相似文献
158.
Filipe Manuel Clemente Rodrigo Ramirez-Campillo Daniel Castillo Javier Raya-Gonzlez Markel Rico-Gonzlez Rafael Oliveira Thomas Rosemann Beat Knechtle 《Biology of sport / Institute of Sport》2022,39(3):765
Plyometric jump training (PJT) can be used for improving balance through bilateral and unilateral jump-landing drills. Since the increased number of articles testing the effects of PJT on dynamic and static balance, it is relevant to summarize the evidence and determine the effects across different original articles. This systematic review with meta-analysis was conducted to assess the effects of PJT programs on dynamic and static balance in soccer players. The data sources utilized were Cochrane, Medline (PubMed), SPORTDiscus, and Web of Science. (i) Soccer players of any age or sex without injury, illness, or other clinical conditions; (ii) PJT-based programs restricted to a minimum of three weeks (duration); (iii) passive or active control groups; (iv) pre-post interventions values of dynamic and/or static balance; (v) randomized-controlled trials; and (vi) peerreviewed original full-text studies written in English, Portuguese, and/or Spanish. The database search initially identified 803 titles. From those, eight articles were eligible for the systematic review and meta-analysis. The results showed no significant differences between PJT and active controls in dynamic anterior, postero-medial, or postero-lateral balance for both left and right legs (p > 0.05). Additionally, no significant differences were found between PJT and active controls in terms of static balance (p = 0.495). The current evidence suggests that PJT has no significant advantage over active control groups in terms of dynamic or static balance. 相似文献
159.
Exogenous polyamines improve rooting of hazel microshoots 总被引:7,自引:0,他引:7
Manuel Rey Carmen Díaz-Sala Roberto Rodríguez 《Plant Cell, Tissue and Organ Culture》1994,36(3):303-308
A strong positive effect of polyamines on rooting of microshoots of adult hazel (Corylus avellana L., cv. Gironell) is described. The effect of polyamines, both in the root induction solution and in the actual rooting medium, was assessed in order to study the effect on the successive rooting phases. Polyamines improved rooting of indole-3-butyric acid-treated microshoots in a synergistic fashion, perhaps by favouring a better induction of roots, with an acceleration of the response (only half the time required for rooting compared to the control). When applied without indole-3-butyric acid, polyamines had only a limited positive effect on rooting, although longer exposure times and/or higher concentrations could increase their effect. Possible rapid uptake and translocation of polyamines in the xylem in our system is discussed. The results offer a new approach to enhance rooting ability of species that are normally difficult to root.Abbreviations BM
basal medium
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid
- NAA
1-naphthaleneacetic acid
- Put
putrescine
- Spd
spermidine
- Spm
spermine 相似文献