Cysteine sulfinic acid (Cys-SO2-) is a protein post-translational modification that is formed reversibly under oxidative conditions. A short, encodable peptide was developed whose metal binding and terbium luminescence are dependent on cysteine (Cys) oxidation to the sulfinic acid. The protein design is based on the modification of a key metal-binding aspartate (Asp) in a canonical EF-Hand motif (DKDADGWISPAEAK) to Cys. In this design, Cys in the thiol oxidation state does not mimic the native Asp, and thus the peptide binds terbium(III) (Tb3+) poorly and exhibits weak terbium luminescence (fluorescence). In contrast, when Cys is oxidized to the Cys sulfinic acid oxoform, the Cys sulfinate effectively mimics Asp, resulting in a significant increase in terbium affinity and luminescence. Asp residues at positions 1, 3, and 5 of the EF-Hand motif were examined as potential sites for Cys oxidation-responsive metal binding. The peptide with Cys at residue 1 exhibited the highest Tb3+ affinity in both oxidation states. The peptide with Cys at residue 3 exhibited a 4.2-fold distinction in affinity between the oxidation states. Most significantly, the peptide with Cys at residue 5 had only modest Tb3+ affinity as the Cys thiol, but exhibited a 30-fold increase in Tb3+ affinity and an 18-fold increase in Tb3+ luminescence on Cys oxidation to the sulfinic acid. This peptide (Ac-DKDACGWISPAEAK-NH2) exhibited selective Tb3+ binding via Cys-SO2- over the thiol, S-glutathionyl, S-nitrosyl, and sulfonic acid oxoforms, indicating substantially greater Lewis basicity of the sulfinate than the sulfonate. NMR spectroscopy and quantum homology modeling indicated that the designed peptide binds metal with an overall geometry similar to that of an EF-Hand motif, with the Cys sulfinate effectively replacing Asp as a metal-binding ligand. This peptide was applied to detect Cys oxidation to the sulfinic acid by fluorescence spectroscopy, suggesting its broader application in understanding Cys sulfinic acid biology.

中文翻译：

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半胱氨酸氧化为亚磺酸可诱导设计肽段中特定于氧仿形式的镧系元素结合和发出荧光。

半胱氨酸亚磺酸（Cys-SO2-）是蛋白质的翻译后修饰，在氧化条件下可逆地形成。已开发出一种可编码的短肽，其金属结合和and发光取决于半胱氨酸（Cys）氧化为亚磺酸的能力。蛋白质设计基于将经典的EF手形基序（DKDADGWISPAEAK）中的关键金属结合天冬氨酸（Asp）修饰为Cys。在这种设计中，巯基氧化态的Cys不能模仿天然的Asp，因此该肽与bind（III）（Tb3 +）的结合较弱，并且weak发光（荧光）弱。相反，当Cys氧化为Cys亚磺酸氧仿时，Cys亚磺酸盐有效模拟Asp，导致b亲和力和发光度显着提高。1、3，和5的EF-手基序被检查为Cys氧化反应金属结合的潜在位点。残基1上具有Cys的肽在两种氧化态下均显示出最高的Tb3 +亲和力。在残基3处具有Cys的肽在氧化态之间的亲和力表现出4.2倍的差异。最显着的是，在残基5处具有Cys的肽仅具有适度的Tb3 +亲和力，如Cys硫醇，但在Cys氧化为亚磺酸时，Tb3 +亲和力提高了30倍，Tb3 +发光度提高了18倍。该肽（Ac-DKDACGWISPAEAK-NH2）通过Cys-SO2-在硫醇，S-谷胱甘肽，S-亚硝酰基和磺酸的氧仿上表现出选择性的Tb3 +结合，表明亚磺酸盐的Lewis碱度明显高于磺酸盐。NMR光谱和量子同源性建模表明，设计的肽以与EF-Hand基序相似的整体几何形状结合金属，Cys亚磺酸盐有效取代了Asp，成为金属结合配体。该肽已用于通过荧光光谱法检测Cys氧化为亚磺酸，表明其在理解Cys亚磺酸生物学方面有更广泛的应用。