Two tales of protein tails: regulation by S100 protein binding and phosphorylation
Pr Laszlo NYITRAY
Eötvös Loránd University, Department of Biochemistry, Budapest, Hungary
Friday, March 15th 2019 - 11 a.m.
- Auditorium, IGBMC
Hosted by Integrated structural Biology, Gilles TRAVE
Protein termini are often unstructured and involved in the regulation of protein function. These intrinsically disordered regions (IDRs) contain many phosphorylation and other PTM sites and also linear motifs responsible for protein-protein interactions (PPIs). PTMs and PPI can regulate protein function synergistically or competitively, and they could even provide isoform-specific regulations. I will present two stories comparing the regulatory effect of phosphorylation and S100 protein binding at terminal IDRs on the function of annexin A2 (ANXA2) and non-muscle myosin 2s (NM2s).
ANXA2 has a versatile role in membrane-associated functions including membrane aggregation, and it is regulated by PTMs and PPIs through an N-tail IDR. Structural studies indicated that the flexibility of the N-tail and the core domain are interrelated and oppositely regulated by Tyr24 and Ser26 phosphorylation, the former being inhibitory to the membrane-bridging function of ANXA2. This negative effect is relieved by S100 binding. Our results provide a structural model for regulation of ANXA2-mediated membrane aggregation by phosphorylation and S100 binding.
NM2 motor protein isoforms (NM2A, -B, -C in mammalian cells) assemble into functional homo- and heterotypic “minifilaments” and are involved in controlling cell adhesion and cell migration. I will show evidence that the equilibrium between these filaments and single molecules can be regulated via S100 protein interactions and phosphorylation at the C-tail IDR. Importantly, S100 proteins can selectively remove NM2A from heterotypic filaments. On the other hand, tail phosphorylation by various kinases down-regulates NM2B filament assembly in an additive fashion and has a comparatively minor effect on NM2A filament stability. These two mutually exclusive mechanisms are likely to contribute to the temporal and spatial sorting of the two NM2 paralogs within heterotypic filaments.