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Titolo:
Heat capacity changes upon burial of polar and nonpolar groups in proteins
Autore:
Loladze, VV; Ermolenko, DN; Makhatadze, GI;
Indirizzi:
Penn State Univ, Coll Med, Dept Biochem & Mol Biol, Hershey, PA 17033 USA Penn State Univ Hershey PA USA 17033 em & Mol Biol, Hershey, PA 17033 USA Russian Acad Sci, AN Bakh Biochem Inst, Moscow 117071, Russia Russian AcadSci Moscow Russia 117071 iochem Inst, Moscow 117071, Russia
Titolo Testata:
PROTEIN SCIENCE
fascicolo: 7, volume: 10, anno: 2001,
pagine: 1343 - 1352
SICI:
0961-8368(200107)10:7<1343:HCCUBO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
HYDROPHOBIC INTERACTION; HUMAN LYSOZYME; CONFORMATIONAL STABILITY; STAPHYLOCOCCAL NUCLEASE; UBIQUITIN MOLECULE; WATER PENETRATION; GENETIC-ANALYSIS; HYDROGEN-BONDS; T4 LYSOZYME; SURFACE;
Keywords:
heat capacity changes; hydration; amino acid substitutions; differential scanning calorimetry; NMR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
60
Recensione:
Indirizzi per estratti:
Indirizzo: Makhatadze, GI Penn State Univ, Coll Med, Dept Biochem & Mol Biol, Hershey, PA 17033 USA Penn State Univ Hershey PA USA 17033 Hershey, PA 17033 USA
Citazione:
V.V. Loladze et al., "Heat capacity changes upon burial of polar and nonpolar groups in proteins", PROTEIN SCI, 10(7), 2001, pp. 1343-1352

Abstract

In this paper we address the question of whether the burial of polar and nonpolar groups in the protein locale is indeed accompanied by the heat capacity changes, DeltaC(p), that have an opposite sign, negative for nonpolar groups acid positive for polar groups. To accomplish this, we introduced amino acid substitutions at four fully buried positions of the ubiquitin molecule (Val5, Val17, Leu67, and Gln41). We substituted Val at positions 5 and17 and Leu at position 67 with a polar residue, Asn. As a control, Ala wasintroduced at the same three positions. We also replaced the buried polar Gln41 with Val and Leu, nonpolar residues that have similar size and shape as Gin. As a control, Asn was introduced at Gln41 as well. The effects of these amino acid substitutions on the stability, and in particular, on the heat capacity change upon unfolding were measured using differential scanning calorimetry. The effect of the amino acid substitutions on the structure was also evaluated by comparing the H-1-N-15 HSQC spectra of the ubiquitin variants. It was found that the Ala substitutions did not have a considerable effect on the heat capacity change upon unfolding. However, the substitutions of aliphatic side chains (Val or Leu) with a polar residue (Asn) leadto a significant (> 30%) decrease in the heat capacity change upon unfolding. The decrease in heat capacity changes does not appear to be the result of significant structural perturbations as seen from the HSQC spectra of the variants. The substitution of a buried polar residue (Gln41) to a nonpolar residue (Leu or Val) leads to a significant (> 25%) increase in heat capacity change upon unfolding. These results indicate that indeed the heat capacity change of burial of polar and nonpolar groups has an opposite sign. However, the observed changes in DeltaC(p) are several times larger than those predicted, based on the changes in water accessible surface area upon substitution.

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Documento generato il 09/04/20 alle ore 10:23:58