Department of Chemistry and Biochemistry, University of California, Santa Cruz, Santa Cruz, California.
Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon.
Biophys J. 2021 Aug 17;120(16):3508-3515. doi: 10.1016/j.bpj.2021.05.008. Epub 2021 May 20.
Membrane proteins often require solubilization to study their structure or define the mechanisms underlying their function. In this study, the functional properties of the membrane protein rhodopsin in its native lipid environment were investigated after being solubilized with styrene-maleic acid (SMA) copolymer. The static absorption spectra of rhodopsin before and after the addition of SMA were recorded at room temperature to quantify the amount of membrane protein solubilized. The samples were then photobleached to analyze the functionality of rhodopsin upon solubilization. Samples with low or high SMA/rhodopsin ratios were compared to find a threshold in which the maximal amount of active rhodopsin was solubilized from membrane suspensions. Interestingly, whereas the highest SMA/rhodopsin ratios yielded the most solubilized rhodopsin, the rhodopsin produced under these conditions could not reach the active (Meta II) state upon photoactivation. The results confirm that SMA is a useful tool for membrane protein research, but SMA added in excess can interfere with the dynamics of protein activation.
膜蛋白通常需要溶解才能研究其结构或确定其功能的机制。在这项研究中，研究了用苯乙烯-马来酸（SMA）共聚物溶解后膜蛋白视紫红质在其天然脂质环境中的功能特性。在室温下记录视紫红质在添加 SMA 前后的静态吸收光谱，以定量溶解的膜蛋白量。然后用光漂白来分析溶解后视紫红质的功能。将低 SMA/视紫红质比和高 SMA/视紫红质比的样品进行比较，以找到从膜悬浮液中溶解最大量活性视紫红质的阈值。有趣的是，尽管最高的 SMA/视紫红质比产生了最多的可溶解视紫红质，但在这些条件下产生的视紫红质在光激活时不能达到活性（Meta II）状态。结果证实 SMA 是膜蛋白研究的有用工具，但过量添加 SMA 会干扰蛋白质激活的动力学。
