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61.
Hunt JF Weinkauf S Henry L Fak JJ McNicholas P Oliver DB Deisenhofer J 《Science (New York, N.Y.)》2002,297(5589):2018-2026
The SecA adenosine triphosphatase (ATPase) mediates extrusion of the amino termini of secreted proteins from the eubacterial cytosol based on cycles of reversible binding to the SecYEG translocon. We have determined the crystal structure of SecA with and without magnesium-adenosine diphosphate bound to the high-affinity ATPase site at 3.0 and 2.7 angstrom resolution, respectively. Candidate sites for preprotein binding are located on a surface containing the SecA epitopes exposed to the periplasm upon binding to SecYEG and are thus positioned to deliver preprotein to SecYEG. Comparisons with structurally related ATPases, including superfamily I and II ATP-dependent helicases, suggest that the interaction geometry of the tandem motor domains in SecA is modulated by nucleotide binding, which is shown by fluorescence anisotropy experiments to reverse an endothermic domain-dissociation reaction hypothesized to gate binding to SecYEG. 相似文献
62.
S. Kinnunen S. Hyypp N. Oksala D.E. Laaksonen M.-L. Hannila C.K. Sen M. Atalay 《Research in veterinary science》2009,87(3):462-467
Heat shock protein (HSP) expression is an adaptive mechanism against the disruption of cell homeostasis during exercise. Several antioxidant supplementation strategies have been used to enhance tissue protection. In this study, we examined the effects of a redox modulator, α-lipoic acid (LA) on HSP responses in six standardbred trotters following intense aerobic exercise. DL–LA supplementation (25 mg kg−1 d−1) for five weeks increased the resting levels of HSP90 (1.02 ± 0.155 in control and 1.26 ± 0.090 after supplementation in arbitrary units) and the recovery levels of inducible HSP70 (0.89 ± 0.056 in control and 1.05 ± 0.089 after supplementation in arbitrary units) in skeletal muscle. Furthermore, LA increased skeletal muscle citrate synthase activity at rest and lowered the blood lactate concentration during exercise without any changes in the heart rate. LA had no effect on concentrations of HSP60, HSP25 or GRP75 in skeletal muscle. LA decreased the exercise-induced increases in plasma aspartate aminotransferase and creatine kinase concentrations during recovery. Our results suggest that LA supplementation may enhance tissue protection and increase oxidative capacity of the muscle in horse. 相似文献