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Titolo:
Structural comparisons of TIM barrel proteins suggest functional and evolutionary relationships between beta-galactosidase and other glycohydrolases
Autore:
Juers, DH; Huber, RE; Matthews, BW;
Indirizzi:
Univ Oregon, Inst Mol Biol, Howard Hughes Med Inst, Eugene, OR 97403 USA Univ Oregon Eugene OR USA 97403 ard Hughes Med Inst, Eugene, OR 97403 USA Univ Oregon, Dept Phys, Eugene, OR 97403 USA Univ Oregon Eugene OR USA 97403 v Oregon, Dept Phys, Eugene, OR 97403 USA
Titolo Testata:
PROTEIN SCIENCE
fascicolo: 1, volume: 8, anno: 1999,
pagine: 122 - 136
SICI:
0961-8368(199901)8:1<122:SCOTBP>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
MAGNETIC-RESONANCE SPECTROSCOPY; SEQUENCE-BASED CLASSIFICATION; CELLULOSE-BINDING DOMAIN; ACTIVE-SITE MOTIFS; CRYSTAL-STRUCTURE; ESCHERICHIA-COLI; GLYCOSYL HYDROLASES; 3-DIMENSIONAL STRUCTURE; BACTERIAL CELLULASE; CATALYTIC DOMAIN;
Keywords:
beta-galactosidase; structural comparison; TIM-barrel proteins;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
60
Recensione:
Indirizzi per estratti:
Indirizzo: Matthews, BW Univ Oregon, Inst Mol Biol, Howard Hughes Med Inst, Eugene, OR 97403 USA Univ Oregon Eugene OR USA 97403 d Inst, Eugene, OR 97403 USA
Citazione:
D.H. Juers et al., "Structural comparisons of TIM barrel proteins suggest functional and evolutionary relationships between beta-galactosidase and other glycohydrolases", PROTEIN SCI, 8(1), 1999, pp. 122-136

Abstract

beta-Galactosidase (lacZ) from Escherichia coli is a 464 kDa homotetramer. Each subunit consists of five domains, the third being an alpha/beta barrel that contains most of the active site residues. A comparison is made between each of the domains and a large set of proteins representative of all structures from the protein data bank. Many structures include an alpha/betabarrel. Those that are most similar to the alpha/beta barrel of E. coli beta-galactosidase have similar catalytic residues and belong to the so-called "4/7 superfamily" of glycosyl hydrolases. The structure comparison suggests that beta-amylase should also be included in this family. Of three structure comparison methods tested, the "ProSup" procedure of Zu-Kang and Sippland the "Superimpose" procedure of Diederichs were slightly superior in discriminating the members of this superfamily, although all procedures were very powerful in identifying related protein structures. Domains 1, 2, and 4 of E. coli beta-galactosidase have topologies related to "jelly-roll barrels" and "immunoglobulin constant" domains. This fold also occurs in the cellulose binding domains (CBDs) of a number of glycosyl hydrolases. The foldof domain 1 of E. coli beta-galactosidase is closely related to some CBDs,and the domain contributes to substrate binding, but in a manner unrelatedto cellulose binding by the CBDs. This is typical of domains 1, 2, 4, and 5, which appear to have been recruited to play roles in beta-galactosidase that are unrelated to the functions that such domains provide in other contexts. It is proposed that beta-galactosidase arose from a prototypical single domain alpha/beta barrel with an extended active site cleft. The subsequent incorporation of elements from other domains could then have reduced the size of the active site from a cleft to a pocket to better hydrolyze the disaccharide lactose and, at the same time, to facilitate the production ofinducer, allolactose.

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Documento generato il 29/11/20 alle ore 02:52:45