Collaborative Research: Elucidating the Influence of Metal Binding on Electronic/Geometric Structure-Function Relationships in Photorespiration

在这个由化学部门生命过程化学项目资助的项目中，康奈尔大学的凯尔·m·兰开斯特教授和加州大学戴维斯分校的阿诺德·j·布鲁姆教授评估了不同金属结合的作用，特别是镁和锰，在光呼吸的机制和生物能量学中，Rubisco是地球上最普遍的蛋白质，与氧气而不是与二氧化碳反应。生物无机光谱学家和植物生理学家之间的合作旨在为过去、现在和未来环境条件下光合作用的进化和植物碳氮平衡之间的关系提供新的视角。这些信息对于维持粮食质量和确保未来几十年的世界粮食安全至关重要。兰开斯特教授和布鲁姆教授通过在线《地球百科全书》中的文章、科学会议上的研讨会（包括一些由STEM职业中代表性不足的科学家协会组织的研讨会）以及编写和保持学生以及与环境变化相关的美国和外国专业人士使用的最新印刷和在线教科书来传播这些信息。拟议的研究涉及广泛的光谱学、动力学和计算技术的应用，以对比锰或镁与光呼吸途径中催化前三个化学步骤的酶结合时的蛋白质结构和植物代谢。用x射线晶体学、电子自旋共振、x射线吸收和磁性圆二色光谱对Rubisco、苹果酸酶和磷酸乙醇酸磷酸酶的Mn2+结合形式进行了表征。对分离的完整叶绿体和光呼吸酶进行了研究。分离叶绿体的工作包括镁和锰浓度的比例染料测量，O2和CO2消耗的光电测量以及光呼吸产物的质谱评估。对分离酶进行的工作包括测量核酮糖-1,5-二磷酸氧化过程中锰Rubisco的电子转移动力学，以及研究潜在的生理相关电子转移伙伴。该研究验证了光呼吸不是一个浪费过程的假设，而是一个产生还原剂以支持硝酸盐和硫酸盐转化为氨基酸的过程。因此，C3固碳可能比先前假设的节能得多。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project funded by the Chemistry of Life Processes Program of the Chemistry Division, Professors Kyle M. Lancaster of the Cornell University and Arnold J. Bloom of the University of California Davis evaluate the role of differential metal binding, specifically magnesium versus manganese, on the mechanisms and bioenergetics of photorespiration in which Rubisco, the most prevalent protein on the planet, reacts with oxygen rather than with carbon dioxide. This collaboration between a bioinorganic spectroscopist and a plant physiologist seeks to provide new perspectives on the evolution of photosynthesis and the relationships between plant carbon and nitrogen balances under past, present, and future environmental conditions. Such information is critical for maintaining food quality and ensuring world food security in the coming decades. Professors Lancaster and Bloom disseminate this information through articles in the online Encyclopedia of Earth, workshops at scientific meetings, including some organized by Societies of scientists who are members of groups underrepresented in STEM careers, and by writing and keeping up-to-date printed and online textbooks used by students as well as by American and foreign professionals whose work is related to environmental change. The proposed research involves application of a broad range of spectroscopic, kinetics, and computational techniques to contrast protein structure and plant metabolism when manganese or magnesium binds to the enzymes that catalyze the first three chemical steps in the photorespiratory pathway. The Mn2+-bound forms of Rubisco, malic enzyme, and phosphoglycolate phosphatase are characterized by X-ray crystallography and by electron spin resonance, X-ray absorption, and magnetic circular dichroism spectroscopy. Both isolated, intact chloroplasts as well as purified photorespiratory enzymes are studied. The work with isolated chloroplasts involves ratiometric dye measurements of magnesium and manganese concentrations, optode measurements of O2 and CO2 consumption, and mass spectrometric assessment of photorespiratory products. Work carried out on isolated enzymes involves measurement of electron transfer kinetics from manganese Rubisco during oxygenation of ribulose-1,5-bisphosphate as well as investigation of potential physiologically relevant electron transfer partners. The research tests the hypothesis that photorespiration is not a wasteful process, but one that generates reductant to support the conversion of nitrate and sulfate into amino acids. Therefore, C3 carbon fixation may be much more energy efficient than previously assumed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.