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Sreevidya Aluvila Rusudan Kotaria Jiakang Sun June A. Mayor D. Eric Walters David H. T. Harrison Ronald S. Kaplan 《The Journal of biological chemistry》2010,285(35):27314-27326
The objective of this study was to identify the role of individual amino acid residues in determining the substrate specificity of the yeast mitochondrial citrate transport protein (CTP). Previously, we showed that the CTP contains at least two substrate-binding sites. In this study, utilizing the overexpressed, single-Cys CTP-binding site variants that were functionally reconstituted in liposomes, we examined CTP specificity from both its external and internal surfaces. Upon mutation of residues comprising the more external site, the CTP becomes less selective for citrate with numerous external anions able to effectively inhibit [14C]citrate/citrate exchange. Thus, the site 1 variants assume the binding characteristics of a nonspecific anion carrier. Comparison of [14C]citrate uptake in the presence of various internal anions versus water revealed that, with the exception of the R189C mutant, the other site 1 variants showed substantial uniport activity relative to exchange. Upon mutation of residues comprising site 2, we observed two types of effects. The K37C mutant displayed a markedly enhanced selectivity for external citrate. In contrast, the other site 2 mutants displayed varying degrees of relaxed selectivity for external citrate. Examination of internal substrates revealed that, in contrast to the control transporter, the R181C variant exclusively functioned as a uniporter. This study provides the first functional information on the role of specific binding site residues in determining mitochondrial transporter substrate selectivity. We interpret our findings in the context of our homology-modeled CTP as it cycles between the outward-facing, occluded, and inward-facing states. 相似文献
915.
Lee HH Meyer EH Goya S Pichavant M Kim HY Bu X Umetsu SE Jones JC Savage PB Iwakura Y Casasnovas JM Kaplan G Freeman GJ DeKruyff RH Umetsu DT 《Journal of immunology (Baltimore, Md. : 1950)》2010,185(9):5225-5235
T cell Ig-like mucin-like-1 (TIM-1) is an important asthma susceptibility gene, but the immunological mechanisms by which TIM-1 functions remain uncertain. TIM-1 is also a receptor for phosphatidylserine (PtdSer), an important marker of cells undergoing programmed cell death, or apoptosis. We now demonstrate that NKT cells constitutively express TIM-1 and become activated by apoptotic cells expressing PtdSer. TIM-1 recognition of PtdSer induced NKT cell activation, proliferation, and cytokine production. Moreover, the induction of apoptosis in airway epithelial cells activated pulmonary NKT cells and unexpectedly resulted in airway hyperreactivity, a cardinal feature of asthma, in an NKT cell-dependent and TIM-1-dependent fashion. These results suggest that TIM-1 serves as a pattern recognition receptor on NKT cells that senses PtdSer on apoptotic cells as a damage-associated molecular pattern. Furthermore, these results provide evidence for a novel innate pathway that results in airway hyperreactivity and may help to explain how TIM-1 and NKT cells regulate asthma. 相似文献
916.
Wen-Quan Zou Jan Langeveld Xiangzhu Xiao Shugui Chen Patrick L. McGeer Jue Yuan Michael C. Payne Hae-Eun Kang John McGeehan Man-Sun Sy Neil S. Greenspan David Kaplan Gong-Xian Wang Piero Parchi Edward Hoover Geoff Kneale Glenn Telling Witold K. Surewicz Qingzhong Kong Jian-Ping Guo 《The Journal of biological chemistry》2010,285(18):13874-13884
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1植物名称狭叶松果菊(Echinacea angustifolia DC.)。
2材料类别种子。 相似文献
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