摘要:

AbstractCompartmentalization of cellular amino acid pools occurs in cultures of cardiac and skeletal muscle cells, but the factors involved in this are not clear. We have further defined this problem by analyzing the intracellular free leucine and the transfer‐RNA‐(tRNA)‐bound leucine pool in cultures of skeletal and cardiac muscle incubated with3H‐leucine in the presence and absence of serum and amino acids. Withdrawal of nitrogen substrates caused substantial changes in leucine pool relationships–in particular, a change in the degree to which intracellular free leucine and tRNA‐leucine were derived from the culture medium. In separate experiments, the validity of our tRNA measurements was confirmed by measurements of the specific activity of newly synthesized ferritin after iron induction. We discuss the implications of these findings with regard‐to factors involved in the control of amino acid flux through the cell, as well as with regard to design of experiments using isotopic amino acids to measure rates of amino aci

ISSN:0730-2312    

DOI:10.1002/jcb.240250302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe specific activities of the alkaline phosphatase (APase), type I phosphodiesterase and 5′‐nucleotidase activities associated with the brush‐border plasma membrane of the tapeworm, Hymenolepis diminuta, decrease significantly as the tapeworm grows and matures. Kinetic analyses of the APase activity associated with membrane preparations from whole 6‐, 12‐, and 18‐d‐old H diminuta, and individual pieces of 18‐d‐old H diminuta cut into ten pieces of equal length, failed to demonstrate qualitative changes in the APase activity. Therefore, the decreased specific activities are apparently due to changes in the ratios of enzymatically active to enzymatically inactive membrane proteins (ie, quantitative changes in the membrane proteins) which occur as t

ISSN:0730-2312    

DOI:10.1002/jcb.240250303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractPhosphoproteins produced by the incubation of crude extracts of Salmonella typhimurium and Escherichia coli with either [32P]phosphoenolpyruvate or [γ32P]ATP have been resolved and detected using sodium dodecyl sulphate poly‐acrylamide gel electrophoresis and autoradiography. Simple techniques were found such that distinctions could be made between phosphoproteins containing acid‐labile or stable phosphoamino acids and between N1‐P‐histidine and N3‐P‐histidine. Phosphoproteins were found to be primarily formed from phosphoenolpyruvate, but because of an efficient phosphoexchange, ATP also led to the formation of the major phosphoenolpyruvate‐dependent phosphoproteins. These proteins had the following apparent subunit molecular weights: 65,000, 65,000, 62,000, 48,000, 40,000, 33,000, 25,000, 20,000, 14,000, 13,000, 9,000, 8,000. Major ATP‐dependent phosphoproteins were detected with apparent subunit molecular weights of 75,000, 46,000, 30,000, and 15,000. Other minor phosphoproteins were detected. The phosphorylation of the 48,000‐ and 25,000‐MW proteins by phos‐phoenolpyruvate was independent of the phosphoenolpyruvate:sugar phospho‐transferase system (PTS). The PTS phosphoproteins were identified as enzyme I (soluble; MW = 65,000); enzyme IIN‐acetylglucosamine(membrane bound; MW = 65,000); enzyme IImannitol(membrane bound; MW = 62,000); IIIfructose(soluble; MW = 40,000); IIImannose(partially membrane associated; MW = 33,000); IIIglucose(soluble; MW = 20,000); IIIglucitol(soluble; MW = 13‐14,000); HPr (soluble; MW = 9,000); FPr (fructose induced HPr‐like protein (soluble; MW = 8,000). HPr and FPr are phosphorylated on the N‐1 position of a histidyl residue while all the others appear to be phosphorylated on an N‐3 position of a histidyl residue. These studies identify some previously unknown proteins of the PTS and show the phosphorylation of others, which although previously known, had no

ISSN:0730-2312    

DOI:10.1002/jcb.240250304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractIn response to a differentiation factor (G‐CSF) the myelomonocytic leukemia cell line (WEHI‐3B(D+) differentiates to form mature macrophages and neutrophils. The effect of G‐CSF on WEHI‐3B(D+) differentiation was augmented by low concentrations (5 ng/ml) of actinomycin D. Quantitative binding of an antineutrophil serum was used to segregate the differentiated cells from the leukemic blast cells. Molecular markers of later myeloid differentiation were detected in myelocytes and macrophages purified from differentiating WEHI‐3B(D+) cells. To study the initial molecular processes associated with the initiation of WEHI‐3B(D+) cells to differentiation, the protein changes were analyzed using gel electrophoresis. Quantitative analysis of the fluorographs from the two‐dimensional (2D) electrophorograms of the35S‐labeled proteins revealed major changes in the biosynthetic rates for 16 proteins within 5 hr: The biosynthesis of six proteins was increased and another ten proteins were synthesized at a reduced rate. Two of the proteins (17K and 36K daltons) were located in the nucleus. Pulse‐chase experiments indicated that protein turnover for these proteins was rapid but the degradation of four proteins was suppressed. At least six of the proteins (16K to 120K daltons) were acidic and were associated with the cytoplasm. Electrophoretic analysis of the35S‐labeled proteins indicated that a 35K protein induced by G‐CSF was found in high abundance only in purified cells of intermediate differentiation (eg, myelocytes). Other proteins (eg, a very high molecular weight protein, and a 16K dalton protein) were obviously late markers of differentiated neutr

ISSN:0730-2312    

DOI:10.1002/jcb.240250305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240250301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY