Duan Yuwei, Niu Weijing, Pang Linlin, Mu Da-Shuai, Du Zong-Jun, Zhang Youming, Bian Xiaoying, Zhong Guannan
Helmholtz International Laboratory for Anti-Infectives, State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
Marine College, Shandong University, Weihai, China.
Front Microbiol. 2023 Jul 10;14:1181125. doi: 10.3389/fmicb.2023.1181125. eCollection 2023.
Lasso peptides are ribosomally synthesized peptides that undergo post-translational modifications including leader peptide removal by B (or the segregated B1 and B2) proteins and core peptide macrolactamization by C proteins to form a unique lariat topology. A conserved threonine residue at the penultimate position of leader peptide is hitherto found in lasso peptide precursors and shown to be a critical recognition element for effective enzymatic processing. We identified a lasso peptide biosynthetic gene cluster () from FA350, a Gram-negative and facultatively prey-dependent bacterium that belongs to a novel bacterial order in the class . The kinase BsfK specifically catalyzes the phosphorylation of the precursor peptide BsfA on the Ser3 residue. BsfB1 performs dual functions to accelerate the post-translational phosphorylation and assist BsfB2 in leader peptide removal. Most importantly, the penultimate residue of leader peptide is an isoleucine rather than the conserved threonine and this isoleucine has a marked impact on the phosphorylation of Ser3 as well as leader peptide removal, implying that BsfB1 and BsfB2 exhibit a new substrate selectivity for leader peptide binding and excision. This is the first experimentally validated penultimate isoleucine residue in a lasso peptide precursor to our knowledge. analysis reveals that the leader peptide Ile/Val(-2) residue is rare but not uncommon in phosphorylated lasso peptides, as this residue is also discovered in and in addition to .
套索肽是核糖体合成的肽，会经历翻译后修饰，包括通过B（或分离的B1和B2）蛋白去除前导肽，以及通过C蛋白进行核心肽大环化以形成独特的套索拓扑结构。迄今在套索肽前体中发现前导肽倒数第二个位置有一个保守的苏氨酸残基，并且它是有效酶促加工的关键识别元件。我们从FA350中鉴定出一个套索肽生物合成基因簇，FA350是一种革兰氏阴性且兼性依赖猎物的细菌，属于该类中的一个新细菌目。激酶BsfK特异性催化前体肽BsfA的Ser3残基磷酸化。BsfB1具有双重功能，可加速翻译后磷酸化并协助BsfB2去除前导肽。最重要的是，前导肽的倒数第二个残基是异亮氨酸而非保守的苏氨酸，并且这种异亮氨酸对Ser3的磷酸化以及前导肽的去除有显著影响，这意味着BsfB1和BsfB2对前导肽的结合和切除表现出一种新的底物选择性。据我们所知，这是套索肽前体中第一个经过实验验证的倒数第二个异亮氨酸残基。分析表明，前导肽Ile/Val（-2）残基在磷酸化套索肽中很少见但并非不常见，因为除了之外，在和中也发现了该残基。
