Identification, modeling, and characterization studies ofTetrahymena thermophilamyosinFERMdomains suggests a conserved core fold but functional differences

Abstract

Myosins (MYO) define a superfamily of motor proteins which facilitate movement along cytoskeletal actin filaments in an ATP-dependent manner. To date, over 30 classes of myosin have been defined that vary in their roles and distribution across different taxa. The multidomain tail of myosin is responsible for the observed functional differences in different myosin classes facilitating differential binding to different cargos. One domain found in this region, the FERM domain, is found in several diverse proteins and is involved in many biological functions ranging from cell adhesion and actin-driven cytoskeleton assembly to cell signaling. Recently, new classes of unconventional myosin have been identified in Tetrahymena thermophila. In this study, we have identified, modeled, and characterized eight FERM domains from the unconventional T. thermophila myosins as their complete functional MyTH4-FERM cassettes. Our results reveal notable sequence, structural, and electrostatic differences between T. thermophila and other characterized FERM domains. Specifically, T. thermophila FERM domains contain helical inserts or extensions, which contribute to significant differences in surface electrostatic profiles of T. thermophila myosin FERMs when compared to the conventional FERM domains. Analyses of the modeled domains reveal differences in key functional residues as well as phosphoinositide-binding signatures and affinities. The work presented here broadens the scope of our understanding of myosin classes and their inherent functions, and provides a platform for experimentalists to design rational experimental studies to test the functional roles for T. thermophila myosins.

In Silico Analysis of a Drosophila Parasitoid Venom Peptide Reveals Prevalence of the Cation–Polar–Cation Clip Motif in Knottin Proteins

“…Consequently, sequence alignments often fall short in investigating the functional potential of proteins such as knottins, where the varied primary structures may obscure shared structure–function relationships. In silico methods facilitate broad analysis of potential structure–function correlations for such interesting folds [ 46 , 47 , 48 , 49 , 50 ]. Our detailed analysis of the LhKNOT structure and its structural homologs supports the idea that this parasite protein has the hallmarks of a knottin peptide with functions in host defense: (a) the closest matches to LhKNOT are antimicrobial peptides; (b) LhKNOT’s Pfam signature describes it as cysteine knotted “antifungal peptide”; and (c) a CPC clip is present.…”