半胱氨酸残迹在蛋白的催化或调控点上经常是活跃的，这是由于它们硫醇侧链是极为亲核的。侧链活性因局部蛋白微环境的不同而有很大差别，但被称为“定量活性分析”的一种新方法（该方法将基于活性的小分子探针与质谱结合在一起）使得测定半胱氨酸残迹的内在活性成为可能。在几种功能未知的蛋白中识别出了活性超强的半胱氨酸，其中包括在所有真核生物中都保留了下来的残迹，它是酵母的存活能力所必需的，也涉及铁-硫蛋白的生物生成。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09472
Quantitative reactivity profiling predicts functional cysteines in proteomes
Eranthie Weerapana,Chu Wang,Gabriel M. Simon,Florian Richter,Sagar Khare,Myles B. D. Dillon,Daniel A. Bachovchin,Kerri Mowen,David Baker& Benjamin F. Cravatt
Cysteine is the most intrinsically nucleophilic amino acid in proteins, where its reactivity is tuned to perform diverse biochemical functions. The absence of a consensus sequence that defines functional cysteines in proteins has hindered their discovery and characterization. Here we describe a proteomics method to profile quantitatively the intrinsic reactivity of cysteine residues en masse directly in native biological systems. Hyper-reactivity was a rare feature among cysteines and it was found to specify a wide range of activities, including nucleophilic and reductive catalysis and sites of oxidative modification. Hyper-reactive cysteines were identified in several proteins of uncharacterized function, including a residue conserved across eukaryotic phylogeny that we show is required for yeast viability and is involved in iron-sulphur protein biogenesis. We also demonstrate that quantitative reactivity profiling can form the basis for screening and functional assignment of cysteines in computationally designed proteins, where it discriminated catalytically active from inactive cysteine hydrolase designs
