Glu-311 in External Loop 4 of the Sodium/Proline Transporter PutP Is Crucial for External Gate Closure.

ABSTRACT: The available structural information on LeuT and structurally related transporters suggests that external loop 4 (eL4) and the outer end of transmembrane domain (TM) 10' participate in the reversible occlusion of the outer pathway to the solute binding sites. Here, the functional significance of eL4 and the outer region of TM10' are explored using the sodium/proline symporter PutP as a model. Glu-311 at the tip of eL4, and various amino acids around the outer end of TM10' are identified as particularly crucial for function. Substitutions at these sites inhibit the transport cycle, and affect in part ligand binding. In addition, changes at selected sites induce a global structural alteration in the direction of an outward-open conformation. It is suggested that interactions between the tip

SUBMITTER: Bracher S 

PROVIDER: S-EPMC4777837 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature