Thu, 21 Aug 2008 15:29:22 BST CiteULike: neils Pascarella http://www.citeulike.org/user/neils/author/Pascarella CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/neils/article/2288264 <i>Protein Eng., Vol. 14, No. 3. (1 March 2001), pp. 141-148.</i><br /><br />A systematic comparative analysis of 21 psychrophilic enzymes belonging to different structural families from prokaryotic and eukaryotic organisms is reported. The sequences of these enzymes were multiply aligned to 427 homologous proteins from mesophiles and thermophiles. The net flux of amino acid exchanges from meso/thermophilic to psychrophilic enzymes was measured. To assign the observed preferred exchanges to different structural environments, such as secondary structure, solvent accessibility and subunit interfaces, homology modeling was utilized to predict the secondary structure and accessibility of amino acid residues for the psychrophilic enzymes for which no experimental three-dimensional structure is available. Our results show a clear tendency for the charged residues Arg and Glu to be replaced at exposed sites on alpha-helices by Lys and Ala, respectively, in the direction from `hot' to `cold' enzymes. Val is replaced by Ala at buried regions in alpha-helices. Compositional analysis of psychrophilic enzymes shows a significant increase in Ala and Asn and a decrease in Arg at exposed sites. Buried sites in beta-strands tend to be depleted of Val. Possible implications of the observed structural variations for protein stability and engineering are discussed. 10.1093/protein/14.3.141 Structural adaptation of enzymes to low temperatures Giulio Gianese Patrick Argos Stefano Pascarella doi:10.1093/protein/14.3.141 Protein Eng., Vol. 14, No. 3. (1 March 2001), pp. 141-148. 2008-01-25T06:43:02-00:00 2001 Protein Eng. 14 3 141 148 adaptation enzyme for-thuber psychrophily structure thermal http://www.citeulike.org/user/neils/article/1592620 <i>FEBS Journal, Vol. 274, No. 17. (September 2007), pp. 4595-4608.</i> Structural adaptation to low temperatures - analysis of the subunit interface of oligomeric psychrophilic enzymes Tronelli Daniele Maugini Elisa Bossa Francesco Pascarella Stefano doi:10.1111/j.1742-4658.2007.05988.x FEBS Journal, Vol. 274, No. 17. (September 2007), pp. 4595-4608. 2007-08-25T18:48:31-00:00 2007 FEBS Journal 1742-464X 274 17 4595 4608 Blackwell Publishing enzyme oligomeric psychrophily structure http://www.citeulike.org/user/neils/article/2288237 <i>Proteins, Vol. 47, No. 2. (1 May 2002), pp. 236-249.</i><br /><br />Enzymes adapted to cold display structures comparable with those of their meso- and thermophilic homologs but are characterized by a higher catalytic efficiency at low temperatures and by thermolability at moderate temperatures. To identify the structural factors responsible of such features, we undertook a systematic comparative analysis of several structural properties in a data set consisting of 7 cold active enzymes belonging to different structural families and 28 related structures from meso/thermophiles representing most of the structural information now available. Only high-resolution and high-quality structures were considered. Properties were calculated and then compared for each pair of 3D structures displaying different temperatures of adaptation using a temperature-weighting scheme. The significance of the resulting differences was evaluated with a statistical method. Results reveal that each protein family adopts different structural strategies to adapt to low temperatures. However, some common trends are observed: the number of ion pairs, the side-chain contribution to the exposed surface, and the apolar fraction of the buried surface show a consistent decrease with decreasing optimal temperatures. Comparative structural analysis of psychrophilic and meso- and thermophilic enzymes. G Gianese F Bossa S Pascarella Proteins, Vol. 47, No. 2. (1 May 2002), pp. 236-249. 2008-01-25T06:32:27-00:00 2002 Proteins 1097-0134 47 2 236 249 enzyme for-thuber mesophily protein psychrophily structure thermal thermophily