Highly homologous proteins exert opposite biological activities by using different interaction interfaces.

Anat Iosub Amir,Assaf Friedler,Tsafi Danieli,Martijn Van Rosmalen,Mario Lebendiker,Guy Mayer

doi:10.1038/srep11629

Abstract

We present a possible molecular basis for the opposite activity of two homologues proteins that bind similar ligands and show that this is achieved by fine-tuning of the interaction interface. The highly homologous ASPP proteins have opposite roles in regulating apoptosis: ASPP2 induces apoptosis while iASPP inhibits it. The ASPP proteins are regulated by an autoinhibitory interaction between their Ank-SH3 and Pro domains. We performed a detailed biophysical and molecular study of the Pro – Ank-SH3 interaction in iASPP and compared it to the interaction in ASPP2. We found that iASPP Pro is disordered and that the interaction sites are entirely different: iASPP Ank-SH3 binds iASPP Pro via its fourth Ank repeat and RT loop while ASPP2 Ank-SH3 binds ASPP2 Pro via its first Ank repeat and the n-src loop. It is possible that by using different moieties in the same interface, the proteins can have distinct and specific interactions resulting in differential regulation and ultimately different biological activities.

Highlights

(Pro) domain, four ankyrin repeats (Ank) and an SH3 domain
The ASPP proteins interact with different apoptosis-related proteins such as the p53 protein family, Bcl[2] and NFκ B2,7,13,20–24. iASPP Pro interacts with iASPP Ank-SH3 in cells and phosphorylation of iASPP by B1/CDK1 on S84 and S113 inhibits this interaction[25]
ASPP2 is regulated by an interaction between its Ank-SH3 domains and Pro domain, which regulates the intermolecular interactions of ASPP2 with its different protein partners by an autoinhibitory mechanism[18,26]

Summary

Introduction

(Pro) domain, four ankyrin repeats (Ank) and an SH3 domain. ASPP2 and ASPP1 contain a putative α -helical domain at their N- termini. In Helicobacter pylori - infected cells, H. pylori protein CagA binds ASPP2, which results in ASPP2 binding to p5328,29 In these cells the interaction of ASPP2 with p53 is inhibited in the presence of ASPP2 726-782, which is derived from ASPP2 Pro, possibly because of this regulatory mechanism[30]. To gain insight into the molecular mechanism behind this difference, we performed a detailed biophysical and molecular study of the Pro – Ank-SH3 interaction in iASPP and compared it to the interaction in ASPP2. Our results show that the Pro-binding regions in iASPP Ank-SH3 are different than the Pro-binding regions in ASPP2 Ank-SH318, revealing selectivity and specificity between the ASPP proteins. This sheds light on the molecular basis for the difference in activity between the ASPP proteins

Methods

Results

Conclusion