BIO SCI D103 Lecture Notes - Lecture 15: Alpha Helix, Beta Sheet, Codocyte

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Sh2 (or any small protein) domain can be shown in 4 ways: polypeptide backbone model, ribbon model, helices = alpha helix, arrows = beta sheets, wire model with amino acid side chains, space filling model. Domain: substructure produced by any contiguous part of a polypeptide chain that can fold independently of the rest of the protein into a compact, stable structure: usually has 40-350 amino acids. Different domains are associated with different functions. Usually protein only has one stable conformation with useful properties. Various members of a protein family often have distinct functions. Structure of one protein modified evolutionarily to perform new functions related ones = families. Domain shuffling: shuffling of protein domains throughout evolution; joining of preexisting domains in new combinations. Multidomain species: accidental joining of dna sequences that encode each domain, creating a new gene. In more complex organisms, proteins have additional domains so can have more functions. Communication between cells mediated by extracellular signal molecules.