Mr4511 from Methylobacterium radiotolerans is a 164 amino acid protein built of a flavin mononucleotide (FMN) binding, blue-light responsive LOV (Light, Oxygen, Voltage) core domain plus flanking regions. In contrast to the majority of LOV domains, Mr4511 lacks a tryptophan residue that was previously identified as a major quencher for the FMN triplet state in photosensitizers for singlet oxygen (SO) engineered from these photoreceptors. Here we show that for Mr4511 it is sufficient to only mutate the reactive cysteine responsible for the photocycle (Cys71) in the native protein to generate an efficient SO photosensitizer: both C71S and C71G variants exhibit SO quantum yields of formation, Φ_Δ, around 0.2 in air-saturated solutions. Under oxygen saturated conditions, Φ_Δ reaches ∼0.5 in deuterated buffer. The introduction of Trp112 in the canonical position for LOV domains dramatically lowers Φ_Δ to values comparable to miniSOG, one of the early FMN binding proteins touted as a SO sensitizer. Besides its SO properties, Mr4511 is also exceedingly robust against denaturation with urea and is more photostable than free FMN.

中文翻译：

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新型细菌LOV蛋白的单突变会产生单线态氧气产生器†

来自耐放射甲基杆菌的4511先生是一种164个氨基酸的蛋白质，由黄素单核苷酸（FMN）结合，蓝光响应LOV（光，氧，电压）核心结构域以及侧翼区域组成。与大多数LOV域相反，Mr 4511缺少色氨酸残基，该残基先前被确定为由这些感光器改造而成的单线态氧（SO）光敏剂中FMN三线态的主要猝灭剂。在这里，我们表明，对于先生4511就足够了仅突变负责在天然蛋白中的光周期（Cys71），以产生一个有效的SO光敏剂的反应性半胱氨酸：C71S和C71G两种变型的形成，表现出的SO量子产率Φ _Δ，在空气饱和溶液中约为0.2。在氧饱和的条件下，Φ _Δ达到在氘化缓冲〜0.5。在LOV域规范位引入Trp112的大幅降低Φ _Δ至与miniSOG，早期FMN结合蛋白吹捧为SO敏化剂的一个值。4511先生除了具有SO的特性外，还具有极强的抵抗尿素变性的能力，并且比游离的FMN更具光稳定性。