Role of the 14‐3‐3 C‐terminal loop in ligand interaction

Abstract

14‐3‐3 proteins are a family of conserved dimeric molecules that interact with a broad range of target proteins, most of which contain phosphoserine/threonine. The amphipathic groove of 14‐3‐3 is the main structural feature involved in mediating its associations. We have studied another domain of 14‐3‐3, the C‐terminal loop, to determine what role it plays in ligand interaction. A truncated form of 14‐3‐3ζ lacking this C‐terminal loop was generated and found to bind with higher affinity than the wild‐type 14‐3‐3ζ protein to the ligands Raf‐1 and Bad. Interestingly, the truncated 14‐3‐3ζ also showed increased association with the 14‐3‐3 binding‐deficient Bad/S136A mutant. Taken together, these data support a role for the C‐terminal loop as a general inhibitor of 14‐3‐3/ligand interactions. This may provide a mechanism by which inappropriate associations with 14‐3‐3 are prevented. Proteins 2002;49:321–325.