Signal Recognition in Lower Organisms: Light-Induced Control of Cell Movement in the Ciliates Blepharisma and Stentor

Abstract

The structure of a protein is critical to its proper function. The proper function of proteins is critical to life itself. What kinds of structures can a polymer made of amino acids adopt? The possibilities are constrained, both by the identity of the amino acid side chains and also by the nature of the amide bond that connects them. Conventionally, the medium-scale structural unit of a polypeptide chain is referred to as its secondary structure. The three secondary structure elements are the alpha helix, the beta-sheet, and the turn. This review examines each type of secondary structure and touches on contemporary research questions regarding secondary structure.