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961.
Peter T. Hallock Sherry Chin Steven Blais Thomas A. Neubert David J. Glass 《Molecular and cellular biology》2016,36(2):262-270
Crk and CrkL are noncatalytic adaptor proteins necessary for the formation of neuromuscular synapses which function downstream of muscle-specific kinase (MuSK), a receptor tyrosine kinase expressed in skeletal muscle, and the MuSK binding protein Dok-7. How Crk/CrkL regulate neuromuscular endplate formation is not known. To better understand the roles of Crk/CrkL, we identified CrkL binding proteins using mass spectrometry and have identified Sorbs1 and Sorbs2 as two functionally redundant proteins that associate with the initiating MuSK/Dok-7/Crk/CrkL complex, regulate acetylcholine receptor (AChR) clustering in vitro, and are localized at synapses in vivo. 相似文献
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963.
Oxidation of [3-13C]propionate was studied in cultured yeast cells, and the distribution of label in the 2- and 3-positions of alanine was detected by 13C NMR. [3-13C]Propionate forms [2-13C]succinyl-CoA in the mitochondria which then enters the citric acid cycle and forms malate through two symmetrical intermediates, succinate and fumarate. If these symmetrical intermediates randomly diffuse from one enzyme to the next in mitochondria as is normally assumed, then 13C labeling in malate C2 and C3 must be equal. However, any direct transfer of metabolites from site to site between succinate thiokinase, succinate dehydrogenase, and fumarase would result in an uneven distribution of 13C in malate C2 and C3 and any molecules derived from malate. Since pyruvate may be derived from malate via the malic enzyme and subsequently converted into alanine by transamination, any 13C asymmetry in alanine C2 and C3 must directly reflect the 13C distribution in the malate pool. During oxidation of [3-13C]propionate, we detect a significant quantity of labeled alanine, where 13C enrichment in C3 is significantly higher than that in C2. Inhibition of succinate dehydrogenase with malonate or creating conditions that increase the chances of a back-reaction (from malate to fumarate) result in a significant decrease in the asymmetric labeling of alanine. Ubiquinone-deficient yeast cells (having only 10% of the oxidative capacity of wild-type cells) could slowly oxidize propionate, but in this case the 13C labeling was equal in the C2 and C3 of alanine, showing that isotope randomization had occurred.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
964.
How strong‐beaked frugivores such as parrots affect other frugivores is poorly understood. This study quantitated six indices of habitat quality for the facultatively frugivorous Bananaquit (Coereba flaveola) using two habitat types and three treatments of habitat quality, namely old growth forest versus citrus orchards in Dominica, the latter habitat type with and without parrot frugivory. The study also controlled for elevation, rainfall and citrus fruit maturity. The results indicate that both the quantity of parrot frugivory and fruit maturity at the time of frugivory influenced the habitat quality for Bananaquits. Their abundance was higher, individuals stored more fat, and parasite loads were lower on farms with more parrot frugivory. Fruit quality mediated the influence of the quantity of parrot frugivory insofar as Bananaquit body condition was tightly correlated with the fruit chemistry at the time of frugivory or harvest. This study provides empirical evidence of a commensal association and underscores the important ecological role of Neotropical psittacines as mediators of habitat quality for other animal. The findings further suggest that loss of these apex consumers may have triggered previously unappreciated trophic cascades, particularly in island ecosystems lacking large mammalian canopy frugivores. 相似文献