Elucidating the role of a π‐helical region in a thermophilic enzyme from a Glycosyl Hydrolase family

Abstract

One of the essential processes that enable organisms from all kingdoms of life to thrive in an extraordinary range of environments is the diversification of protein function. The α-helices are a dominant secondary structure in proteins and are defined by main-chain hydrogen bonds between residues four apart in sequence whereas π-helices are a secondary structure with H-bonds between residues five apart in sequence. Formally annotated π-helices are rare in protein structure but have been correlated with protein function. π-helices are evolutionarily derived by the insertion of a single amino acid into an α-helix. Several reports have published about the role of π-helix in the protein function. For instance, in mercuric ion reductases, an α- to π-helix conversion due to the insertion of a single residue in α-helix results in positioning a key catalytic tyrosine residue in the mercury binding site. A GH4 homolog from the hyperthermophile Thermotogae contains a π-helical region that is involved in the dimer interface interactions of the protein. In order to evaluate the role of the π-helix in biochemical and biophysical properties of the enzyme, a deletion mutant was produced by site-directed mutagenesis to convert existing π-helix into α-helix. Although the catalytic activity of the deletion mutant remained the same as that of the wild-type, a significant effect was observed in the thermal stability of the mutant. The crystal structure of the mutant was determined to provide the structural basis of the effect on the stability properties. Results from these studies will be presented. An α-helix is generated by the deletion of one amino acid as shown. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.