Human Cellular Retinol Binding Protein II Forms a Domain‐Swapped Trimer Representing a Novel Fold and a New Template for Protein Engineering. (14th August 2020) - Ghanbarpour, Alireza
Abstract: Domain‐swapping is a mechanism for evolving new protein structure from extant scaffolds, and has been an efficient protein‐engineering strategy for tailoring functional diversity. However, domain swapping can only be exploited if it can be controlled, especially in cases where various folds can coexist. Herein, we describe the structure of a domain‐swapped trimer of the iLBP family member hCRBPII, and suggest a mechanism for domain‐swapped trimerization. It is further shown that domain‐swapped trimerization can be favored by strategic installation of a disulfide bond, thus demonstrating a strategy for fold control. We further show the domain‐swapped trimer to be a useful protein design template by installing a high‐affinity metal binding site through the introduction of a single mutation, taking advantage of its threefold symmetry. Together, these studies show how nature can promote oligomerization, stabilize a specific oligomer, and generate new function with minimal changes to the protein sequence. Abstract : Protein fold control : The domain‐swapping folding pathway of human cellular retinol binding protein II has been controlled, and the resulting domain‐swapped trimer made into a metal binding protein, with a minimum of amino acid changes, by using structure‐guided protein design. This illustrates maximally economic evolution of both structure and function.