Protein gene duplication

FIGURE 10.18 A model for the structure of the a-factor transport protein in the yeast plasma membrane. Gene duplication has yielded a protein with two identical halves, each half containing six transmembrane helical segments and an ATP-binding site. Like the yeast a-factor transporter, the multidrug transporter is postulated to have 12 transmembrane helices and 2 ATP-binding sites. 

Higher organisms often elaborate several physically distinct versions of a given enzyme, each of which catalyzes the same reaction. Like the members of other protein families, these protein catalysts or isozymes arise through gene duplication. Isozymes may exhibit subtle differences in properties such as sensitivity to... 

The evolutionary development of starter types, from which proteins later evolved via gene duplication and mutation... 

Homo sapiens (compared to Drosophila melanogaster) Large-scale gene duplications with substantial expansion of genes involved in acquired immune response (B cells, T cells, major histocompatibility complex genes, cytokines, chemokines and their receptors), plasma proteases (complement and hemostatic proteins), proteins associated with apoptotic regulation and proteins related to neuronal network formation and electrical coupling... 

Most sequences belong to multigene families. These are proteins that have evolved by gene duplication, usually followed by specialization of function. There will be a group of homologous proteins, all of which... 

Teichmann, S. A., Park, J., and Chothia, C. (1998). Structural assignments to the Mycoplasma genitalium proteins show extensive gene duplications and domain rearrangements. Proc. Natl. Acad. Sd. U.S.A. 95, 14658—14663. 

For proteins with more than two domains, each potential duplication is listed separately e.g., a minimum of two duplications would be necessary to produce either a three-domain or a four-domain structure. Members of the pairs in the left-hand column both fall within the same structural subcategory and have fairly similar topologies such pairs are perhaps the result of internal gene duplications. Members of pairs in the right-hand column almost all fall into different major categories of tertiary structure (e.g., one all-helical and one antiparallel jS) presumably they could not have been produced by internal gene duplication. 

Fig. 108. Hexokinase domains 1 and 2 the proteins whose domains are least alike of all the cases that may represent gene duplications. The equivalent portions of the two domains are shown shaded.

Proteins containing two 4Fe 4S clusters, typified by the P. aerogenes ferredoxin (PaFd), show striking sequence similarities between the amino- and carboxy-terminal halves of the molecule, suggesting that these proteins evolved by gene duplication of a more primitive protein (Section I,E,3). Of particular note is the pattern of four cysteines in the two halves of the molecule (Cys-8, -11, -14, -18 and Cys-35, -38, -41, -45 in the amino- and carboxyl-terminal halves, respectively, of the PaFd se-... 

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