Cino, E. A. | bioRxiv Science

bioRxiv2021

Lipid distributions and transleaflet cholesterol migration near heterogeneous surfaces in asymmetric bilayers

Specific and nonspecific protein-lipid interactions in cell membranes have important roles in an abundance of biological functions. We have used coarse-grained (CG) molecular dynamics (MD) simulations to assess lipid distributions and cholesterol flipping dynamics around surfaces in a model asymmetric plasma membrane containing one of six structurally distinct entities: aquaporin-1 (AQP1), the bacterial {beta}-barrel outer membrane proteins OmpF and OmpX, KcsA potassium channel, WALP23 peptide, and a carbon nanotube (CNT). Our findings revealed varied lipid partitioning and cholesterol flipping times around the different solutes, and putative cholesterol binding sites in AQP1 and KcsA. The results suggest that protein-lipid interactions can be highly variable, and that surface-dependant lipid profiles are effectively manifested in CG simulations with the Martini force field.

biophysics↗

bioRxiv2020

SS3D: Sequence similarity in 3D for comparison of protein families

Homologous proteins are often compared by pairwise sequence alignment, and structure superposition if the atomic coordinates are available. Unification of sequence and structure data is an important task in structural biology. Here, we present Sequence Similarity 3D (SS3D), a new method for integrating sequence and structure information for comparison of homologous proteins. SS3D quantifies the spatial similarity of residues within a given radius of homologous through-space contacts. The spatial alignments are scored using native BLOSUM and PAM substitution matrices. This work details the SS3D approach and demonstrates its utility through case studies comparing members of several protein families: GPCR, p53, kelch, SUMO, and SARS coronavirus spike protein. We show that SS3D can more clearly highlight biologically important regions of similarity and dissimilarity compared to pairwise sequence alignments or structure superposition alone. SS3D is written in C++, and is available with a manual and tutorial at https://github.com/0x462e41/SS3D/.

bioinformatics↗