Conjugative pili are important in mediating bacterial conjugation and horizontal gene transfer. Since plasmid transfer can include antibiotic-resistance genes, conjugation is an important mechanism in the spread of antibiotic resistance. Filamentous bacteriophages have been shown to exist in two different structural classes: those with a 5-fold rotational symmetry and those with a one-start helix with approximately 5 subunits per turn. Structures for the F and the F-like pED208 conjugation pilus have shown that they have 5-fold rotational symmetry. Here, we report the cryoelectron-microscopic structure of conjugative pili from carbapenem-resistant Klebsiella pneumoniae, encoded on the IncFIIK pKpQIL plasmid, at 3.9 Å resolution and show that it has a one-start helix. These results establish that conjugation pili can exist in at least two structural classes, consistent with other results showing that relatively small perturbations are needed to change the helical symmetry of polymers.

结合菌毛在介导细菌结合和水平基因转移中很重要。由于质粒转移可能包括抗生素抗性基因，因此偶联是抗生素抗性传播的重要机制。已经显示丝状噬菌体存在于两种不同的结构类别中：具有 5 倍旋转对称性的那些和具有每圈大约 5 个亚基的单头螺旋的那些。F 和 F 样 pED208 共轭菌毛的结构表明它们具有 5 倍旋转对称性。在这里，我们报告了来自耐碳青霉烯类肺炎克雷伯菌的结合菌毛的低温电子显微镜结构，在 IncFIIK pKpQIL 质粒上编码，分辨率为 3.9 Å，表明它具有单头螺旋。这些结果表明共轭菌毛可以存在于至少两种结构类别中，这与其他结果一致，表明需要相对较小的扰动来改变聚合物的螺旋对称性。