Solution NMR backbone assignment of the SASH1 SLy proteins associated disordered region (SPIDER).

SASH1 is a scaffold protein with context-dependent biological functions in cell adhesion, tumor metastasis, lung development, and pigmentation. As a member of the SLy protein family, it contains the conserved SLY, SH3, and SAM domains. The 19 kDa SLY domain harbors over 70% of the SASH1 variants associated with pigmentation disorders. However, its solution structure or dynamics have not been investigated yet, and its exact position in the sequence is not clearly defined. Based on the bioinformatic and experimental evidence, we propose renaming this region to the SLy Proteins Associated Disordered Region (SPIDER) and defining the exact position to be amino acids 400-554 of SASH1. We have previously identified a variant in this region linked to a pigmentation disorder, S519N. Here, we used a novel deuteration technique, a suite of TROSY-based 3D NMR experiments, and a high-quality HNN to obtain near complete solution backbone assignment of SASH1's SPIDER. A comparison with the chemical shifts of non-variant (S519) SPIDER shows that the S519N substitution does not alter the free form solution structural propensities of SPIDER. This assignment is the first step to characterize the role of SPIDER in SASH1-mediated cellular functions and provides a model for the future study of sister SPIDER domains in the SLy protein family.