Mobile barrier mechanisms for Na⁺-coupled symport in an MFS sugar transporter.

ABSTRACT: While many 3D structures of cation-coupled transporters have been determined, the mechanistic details governing the obligatory coupling and functional regulations still remain elusive. The bacterial melibiose transporter (MelB) is a prototype of the Na⁺-coupled major facilitator superfamily transporters. With a conformational nanobody (Nb), we determined a low-sugar affinity inward-facing Na⁺-bound cryoEM structure. Collectively with the available outward-facing sugar-bound structures, both the outer and inner barriers were localized. The N- and C-terminal residues of the inner barrier contribute to the sugar selectivity pocket. When the inner barrier is broken as shown in the inward-open conformation, the sugar selectivity pocket is also broken. The binding assays by

SUBMITTER: Hariharan P 

PROVIDER: S-EPMC10542114 | biostudies-literature | 2023 Nov

REPOSITORIES: biostudies-literature