Mannose transporters constitute a superfamily (Man-PTS) of the Phosphoenolpyruvate Carbohydrate Phosphotransferase System (PTS). The membrane complexes are homotrimers of protomers consisting of two subunits, IIC and IID. The two subunits without recognizable sequence similarity assume the same fold, and in the protomer are structurally related by a two fold pseudosymmetry axis parallel to membrane-plane (Liu et al. (2019) Cell Research 29 680). Two reentrant loops and two transmembrane helices of each subunit together form the N-terminal transport domain. Two three-helix bundles, one of each subunit, form the scaffold domain. The protomer is stabilized by a helix swap between these bundles. The two C-terminal helices of IIC mediate the interprotomer contacts. PTS occur in bacteria and archaea but not in eukaryotes. Man-PTS are abundant in Gram-positive bacteria living on carbohydrate rich mucosal surfaces. A subgroup of IICIID complexes serve as receptors for class IIa bacteriocins and as channel for the penetration of bacteriophage lambda DNA across the inner membrane. Some Man-PTS are associated with host-pathogen and -symbiont processes.

甘露糖转运蛋白构成磷酸烯醇丙酮酸碳水化合物磷酸转移酶系统（PTS）的超家族（Man-PTS）。膜复合物是由两个亚基IIC和IID组成的启动子同源三聚体。没有可识别的序列相似性的两个亚基假定具有相同的折叠，并且在原胞中通过平行于膜平面的两倍假对称轴在结构上相关（Liu等人（2019）Cell Research 29680）。每个亚基的两个折返环和两个跨膜螺旋共同形成N末端转运域。两个三螺旋束（每个亚基之一）形成支架结构域。通过在这些束之间的螺旋交换来稳定前驱体。IIC的两个C末端螺旋介导了质子间接触。PTS发生在细菌和古细菌中，但不在真核生物中。Man-PTS富含生活在富含碳水化合物的粘膜表面的革兰氏阳性细菌中。IICIID复合物的一个亚组用作IIa类细菌素的受体，并作为噬菌体λDNA穿过内膜的通道。一些Man-PTS与宿主病原体和-symbiont过程相关。