Structure and Function of Vacuolar H-Adenosine Triphosphatase and H-Pyrophosphatase from Etiolated Mung Bean Seedlings

• Main Authors: Chi Meng Tzeng, 曾驥孟
• Other Authors: Rong-Long Pan
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/sdhxkg

博士 === 國立清華大學 === 輻射生物研究所 === 81 === All these probes caused marked inactivation of enzyme activities of both membrane-bound and solubilized ATPases and its associated protontranslocation.Thebin ding sites were shown to locateat catalytic domain of A TPase by protection and labeling studies.Thedouble-loga rithmic plots of apparent rate constantsversus modifier concentrations gave slopes of approximately one indica ting that atleast one copy ofessential lysine, cystein e, and arginine residue were located at the active site of the catalytic subunit of tonoplast ATPase. A tentat ive architecture at nucleotide binding site of vacuolar ATPase was proposed based on these results. From the quenching parameters,we demonstrated that majo rities of aromatic groups were buried in a relatively h ydrophobic core. From thermodynamic studies,there are a t least two conformational states for ATPase. Substrate -binding of ATPase stabilized the enzyme structureby in crease intheactivation energy from 20.6to 25.9KJ/mol. W e believed that the conformation of the enzyme was alte red to protect against the thermoinactivation. In contr ast,the modification of ATPase byfluorescein 5''-isothio cyanate could accelerate theinhibition by heat. The spa tial arrangement and the relationship of structure and function in the catalytic region ofATPase were studied.