Propensity for C-terminal domain swapping correlates with increased regional flexibility in the C-terminus of RNase A

✍ Scribed by Katherine H. Miller; Susan Marqusee

• Book ID: 105356717
• Publisher: Cold Spring Harbor Laboratory Press
• Year: 2011
• Tongue: English
• Weight: 347 KB
• Volume: 20
• Category: Article
• ISSN: 0961-8368
• DOI: 10.1002/pro.708

✦ Synopsis

Abstract

Domain swapping is a type of oligomerization in which monomeric proteins exchange a structural element, resulting in oligomers whose subunits recapitulate the native, monomeric fold. It has been implicated as a potential mechanism for protein aggregation, which provides a strong impetus to understand the structural determinants and folding mechanisms that trigger domain swapping. Bovine pancreatic ribonuclease A (RNase A) is a well‐studied protein known to domain swap under extreme conditions, such as lyophilization from acetic acid. The major domain‐swapped dimer form of RNase A exchanges a β‐strand at its C‐terminus to form a C‐terminal domain‐swapped dimer. To study the mechanism by which C‐terminal swapping occurs, we used a variant of RNase A containing a P114G mutation that readily domain swaps under physiological conditions. Using NMR and hydrogen–deuterium exchange, we find that the P114G variant has decreased protection from hydrogen exchange compared to the wild‐type protein near the C‐terminal hinge region. Our results suggest that domain swapping occurs via a local high‐energy fluctuation at the C‐terminus.