The structural and biochemical characterization of UNC119B cargo binding and release mechanisms

Yelland, T., Garcia, E., Samarakoon, Y. and Ismail, S. (2021) The structural and biochemical characterization of UNC119B cargo binding and release mechanisms. Biochemistry, 60(25), pp. 1952-1963. (doi: 10.1021/acs.biochem.1c00251) (PMID:34130453) (PMCID:PMC8246649)

Abstract

Two paralogs of the guanine dissociation inhibitor-like solubilizing factors UNC119, UNC119A and UNC119B, are present in the human genome. UNC119 binds to N-myristoylated proteins and masks the hydrophobic lipid from the hydrophilic cytosol, facilitating trafficking between different membranes. Two classes of UNC119 cargo proteins have been classified: low affinity cargoes, released by the Arf-like proteins ARL2 and ARL3, and high affinity cargoes, which are specifically released by ARL3 and trafficked to either the primary cilium or the immunological synapse. The UNC119 homologues have reported differences in functionality, but the structural and biochemical bases for these differences are unknown. Using myristoylated peptide binding and release assays, we show that peptides sharing the previously identified UNC119A high affinity motif show significant variations of binding affinities to UNC119B of up to 427-fold. Furthermore, we solve the first two crystal structures of UNC119B, one in complex with the high affinity cargo peptide of LCK and a second one in complex with the release factor ARL3. Using these novel structures, we identify a stretch of negatively charged amino acids unique to UNC119B that may undergo a conformational change following binding of a release factor which we propose as an additional release mechanism specific to UNC119B.

• Item Type: Articles
• Additional Information: This work was supported by Cancer Research UK core funding number A17196.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Samarakoon, Youhani and Garcia Gonzalez, Dr Esther and Ismail, Dr Shehab
• Authors: Yelland, T., Garcia, E., Samarakoon, Y., and Ismail, S.
• College/School: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Journal Name: Biochemistry
• Publisher: American Chemical Society
• ISSN: 0006-2960
• ISSN (Online): 1520-4995
• Published Online: 15 June 2021
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in Biochemistry 60(25): 1952-1963
• Publisher Policy: Reproduced under a Creative Commons License