Department of Genome Sciences, University of Washington, Seattle, WA 98195;
Department of Biochemistry, University of Washington, Seattle, WA 98195.
Proc Natl Acad Sci U S A. 2018 Feb 6;115(6):1310-1315. doi: 10.1073/pnas.1709061115. Epub 2018 Jan 18.
Protein evolution is driven by the sum of different physiochemical and genetic processes that usually results in strong purifying selection to maintain biochemical functions. However, proteins that are part of systems under arms race dynamics often evolve at unparalleled rates that can produce atypical biochemical properties. In the marine mollusk abalone, lysin and vitelline envelope receptor for lysin (VERL) are a pair of rapidly coevolving proteins that are essential for species-specific interactions between sperm and egg. Despite extensive biochemical characterization of lysin-including crystal structures of multiple orthologs-it was unclear how sites under positive selection may facilitate recognition of VERL. Using a combination of targeted mutagenesis and multidimensional NMR, we present a high-definition solution structure of sperm lysin from red abalone (). Unapparent from the crystallography data, multiple NMR-based analyses conducted in solution reveal clustering of the N and C termini to form a nexus of 13 positively selected sites that constitute a VERL binding interface. Evolutionary rate was found to be a significant predictor of backbone flexibility, which may be critical for lysin bioactivity and/or accelerated evolution. Flexible, rapidly evolving segments that constitute the VERL binding interface were also the most distorted regions of the crystal structure relative to what was observed in solution. While lysin has been the subject of extensive biochemical and evolutionary analyses for more than 30 years, this study highlights the enhanced insights gained from applying NMR approaches to rapidly evolving proteins.
蛋白质进化是由不同的物理化学和遗传过程驱动的，这些过程通常会导致强烈的纯化选择，以维持生化功能。然而，作为军备竞赛动态系统一部分的蛋白质通常以无与伦比的速度进化，从而产生非典型的生化特性。在海洋软体动物鲍鱼中，溶菌酶和溶菌酶卵黄包膜受体（VERL）是一对快速协同进化的蛋白质，对于精子和卵子之间的物种特异性相互作用至关重要。尽管对溶菌酶进行了广泛的生化特性分析，包括多个同源物的晶体结构，但尚不清楚正选择位点如何促进 VERL 的识别。我们使用靶向诱变和多维 NMR 的组合，呈现了来自红鲍（）的精子溶菌酶的高清晰度溶液结构。从晶体学数据中不明显的是，在溶液中进行的多个基于 NMR 的分析揭示了 N 和 C 末端的聚类，形成了一个由 13 个正选择位点组成的连接体，构成了 VERL 结合界面。进化率被发现是骨架灵活性的重要预测因子，这对于溶菌酶的生物活性和/或加速进化可能至关重要。构成 VERL 结合界面的灵活、快速进化的片段也是晶体结构中相对于溶液中观察到的最扭曲的区域。虽然溶菌酶已经成为 30 多年来广泛的生化和进化分析的主题，但这项研究强调了应用 NMR 方法来研究快速进化蛋白质所获得的增强见解。
