Amino acid sequences properties

Given a large population of individuals, a considerable number of sequence variants can be found for a protein. These variants are a consequence of mutations in a gene (base substitutions in DNA) that have arisen naturally within the population. Gene mutations lead to mutant forms of the protein in which the amino acid sequence is altered at one or more positions. Many of these mutant forms are neutral in that the functional properties of the protein are unaffected by the amino acid substitution. Others may be nonfunctional (if loss of function is not lethal to the individual), and still others may display a range of aberrations between these two extremes. The severity of the effects on function depends on the nature of the amino acid substitution and its role in the protein. These conclusions are exemplified by the more than 300 human... 

Lohmann V, Komer F, Herian U, Bartenschlager R (1997) Biochemical properties of hepatitis C vims NS5B RNA-dependent RNA polymerase and identification of amino acid sequence motifs essential for enzymatic activity. J Virol 71 8416-8428... 

The functions of a large proportion of the proteins encoded by the human genome are presently unknown. Recent advances in bioinformatics permit researchers to compare amino acid sequences to discover clues to potential properties, physiologic roles, and mechanisms of action of proteins. Algorithms exploit the tendency of nature to employ variations of a structural theme to perform similar functions in several proteins (eg, the Rossmarm nucleotide binding fold to bind NAD(P)H,... 

A Pstl-HinA (1.2 kbp) fragment was subcloned in pUC19. The enzyme produced by the E. coli transformant was purified fo homogeneify and shown to be identical to that of the original strain. Both enzymes had the same enzymological properties and N-terminal amino acid sequences. ... 

Changing the amino acid sequence of the cloned receptors by mutating nucleotides within the receptor cDNAs has proven to be an effective mechanism by which to identify structural features of the receptors responsible for their unique functional properties. In particular, site-directed mutagenesis has been employed to determine the ligand binding domains of each opiate receptor. 

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