[论文解读] Evolutionary and Structural Constraints Define a Mutation-Resistant Catalytic Core in E. coli Serine Hydroxy methyltransferase (SHMT)

D. Surabhi Pandey, Dwipanjan Sanyal+3 more|arXiv (Cornell University)|Jan 2, 2026

Biochemical and Molecular Research被引用 0

一句话总结

该论文使用多尺度计算框架显示大肠杆菌SHMT的催化核心极为保守、紧密相连且变异受限，与外围区域不同，解释了其被抗生素针对性有限的原因。

ABSTRACT

Serine hydroxymethyltransferase is an essential enzyme in the Escherichia coli folate pathway, yet it has not been adopted as an antibacterial target, unlike DHFR, DHPS, or thymidylate synthase. To investigate this discrepancy, we applied a multi-scale computational framework that integrates large-scale sequence analysis of 1000 homologs, coevolutionary interaction mapping, structural community analysis, intrinsic disorder profiling, and adaptive fitness modelling. These analyses converge on a single conclusion: the catalytic core of SHMT forms an exceptionally conserved and tightly coupled structural unit. This region exhibits dense coevolution, strong intramolecular connectivity, minimal disorder, and extremely low mutational tolerance. Peripheral loops and termini, in contrast, are far more flexible. Relative to established folate-pathway antibiotic targets, SHMT active site is even more rigid and evolutionarily constrained. This extreme constraint may limit the emergence of resistance-compatible mutations, providing a plausible explanation for the absence of natural-product inhibitors. Fitness trajectory modelling supports this interpretation, showing that nearly all active-site residues tolerate only rare or neutral substitutions. Together, these findings identify SHMT as a structurally stable and evolutionarily restricted enzyme whose catalytic architecture is unusually protected. This makes SHMT an underexplored yet promising target for the rational design of next-generation antibacterial agents.

研究动机与目标

• 理解为什么 SHMT 尽管在叶酸通路中是必需的，却不是常见的抗菌靶标的原因。
• 确定定义 SHMT 催化核心的进化与结构约束。
• 评估 SHMT 的突变耐受性以解释潜在的耐药性出现。
• 将 SHMT 活性位点的刚性与其他叶酸通路靶标进行比较，以评估药物设计前景。

提出的方法

• 将对约1000个 SHMT 同源体的大规模序列分析整合在一起。
• 应用共同进化相互作用映射以识别耦合残基。
• 使用结构社区分析和内在无序性分析。
• 实现自适应适应性适能建模以模拟突变对功能的影响。
• 综合结果以表征催化核心与外围区域的差异。

实验结果

研究问题

• RQ1 在大肠杆菌中，SHMT 催化核心受哪些进化与结构约束？
• RQ2 SHMT 活性位点相对于外围区域的突变耐受性有多大？
• RQ3 与其他叶酸通路靶标相比，SHMT 是否在进化约束和结构刚性方面更强，这对药物设计有何启示？

主要发现

• 催化核心在结构上极为保守且紧密耦合。
• 核心区内存在密集的共进化和强烈的分子内连接性。
• 催化核心表现出极少的无序性和极低的突变耐受性。
• 外围环和末端比核心更具柔性。
• 相较于其他叶酸通路靶标，SHMT 的活性位点在进化约束和刚性方面更强。
• 适应性适能轨迹建模表明大多数活性位点残基仅耐受罕见或中性替代。