EnkT is an ATP-binding cassette (ABC) transporter produced by Enterococcus faecium NKR-5-3, which is responsible for the secretion of multiple bacteriocins; enterocins NKR-5-3A, C, D, and Z (Ent53A, C, D, and Z). EnkT has been shown to possess a tolerant recognition mechanism that enables it to secrete the mature Ent53C from a chimeric precursor peptide containing the leader peptide moieties that are derived from different heterologous bacteriocins. In this study, to further characterize EnkT, we aimed to investigate the capacity of EnkT to recognize, process, and secrete non-cognate bacteriocins, which belong to different subclasses of class II. For this, the non-cognate bacteriocin precursor peptides, including enterocin A, pediocin PA-1, lactococcin Q, lactococcin A, and lacticin Q were co-expressed with EnkT, and thereafter, the production of the mature forms of these non-cognate bacteriocins was assessed. Our results revealed that EnkT could potentially recognize, process, and secrete the non-cognate bacteriocins with an exception of the leaderless bacteriocin, lacticin Q. Moreover, the processing and secretion efficiencies of these heterologous non-cognate bacteriocins by EnkT were further enhanced when the leader peptide moiety was replaced with the Ent53C leader peptide (derived from a native NKR-5-3 bacteriocin). The findings of this study describe the wide substrate tolerance of this ABC transporter, EnkT, that can be exploited in the future in establishing effective bacteriocin production systems adaptive to complex fermentation conditions common in many food systems.

EnkT是粪肠球菌产生的ATP结合盒（ABC）转运蛋白NKR-5-3，负责多种细菌素的分泌；肠球菌NKR-5-3A，C，D和Z（Ent53A，C，D和Z）。已显示EnkT具有耐受性识别机制，使其能够从含有衍生自不同异源细菌素的前导肽部分的嵌合前体肽中分泌成熟的Ent53C。在这项研究中，为了进一步表征EnkT，我们旨在研究EnkT识别，加工和分泌属于II类不同亚类的非同源细菌素的能力。为此，将非关联的细菌素前体肽，包括肠球菌素A，pediocin PA-1，乳球菌素Q，乳球菌素A和乳酸菌素Q与EnkT共表达，然后，生成这些非关联蛋白的成熟形式评估细菌素。我们的结果表明，除了无引线的细菌素乳酸菌素Q以外，EnkT可以潜在地识别，加工和分泌非同源细菌素。此外，当前导肽部分被替换为Ent53C前导肽（来自天然NKR-5-3细菌素）。这项研究的发现描述了这种ABC转运蛋白EnkT具有广泛的底物耐受性，将来可用于建立有效的细菌素生产系统，以适应许多食品系统中常见的复杂发酵条件。当将前导肽部分替换为Ent53C前导肽（源自天然NKR-5-3细菌素）时，通过EnkT进一步增强了这些异源非同源细菌素的加工和分泌效率。这项研究的发现描述了这种ABC转运蛋白EnkT具有广泛的底物耐受性，将来可用于建立有效的细菌素生产系统，以适应许多食品系统中常见的复杂发酵条件。当将前导肽部分替换为Ent53C前导肽（源自天然NKR-5-3细菌素）时，通过EnkT进一步增强了这些异源非同源细菌素的加工和分泌效率。这项研究的发现描述了这种ABC转运蛋白EnkT具有广泛的底物耐受性，将来可用于建立有效的细菌素生产系统，以适应许多食品系统中常见的复杂发酵条件。