title: Molecular bases of protein halotolerance.
abstract: Halophilic proteins are stable and function at high salt concentration. Understanding how these molecules maintain their fold stable and avoid aggregation under harsh conditions is of great interest for biotechnological applications. This mini-review describes what is known about the molecular determinants of protein halotolerance. Comparisons between the sequences of halophilic/non-halophilic homologous protein pairs indicated that Asp and Glu are significantly more frequent, while Lys, Ile and Leu are less frequent in halophilic proteins. Homologous halophilic and non-halophilic proteins have similar overall structure, secondary structure content, and number of residues involved in the formation of H-bonds. On the other hand, on the halophilic protein surface, a decrease of nonpolar residues and an increase of charged residues are observed. Particularly, halophilic adaptation correlates with an increase of Asp and Glu, compensated by a decrease of basic residues, mainly Lys, on protein surface. A thermodynamic model, that provides a reliable explanation of the salt effect on the conformational stability of globular proteins, is presented.
authors.affiliation: Dipartimento di Scienze e Tecnologie, Università del Sannio, Benevento, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Graziano
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Napoli 'Federico II', Napoli, Italy; Istituto di Biostrutture e Bioimmagini, CNR, Napoli, Italy. Electronic address: antonello.merlino@unina.it.
authors.forename: Antonello
authors.initials: A
authors.lastname: Merlino
mesh_terms: D000222:Adaptation, Physiological; D024342:Amino Acids, Acidic / Q000737:chemistry* / Q000378:metabolism; D024361:Amino Acids, Basic / Q000737:chemistry* / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000737:chemistry* / Q000378:metabolism; D019143:Evolution, Molecular; D006860:Hydrogen Bonding; D008958:Models, Molecular; D055550:Protein Stability; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D054712:Salinity; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D024342:Amino Acids, Acidic; D024361:Amino Acids, Basic; D000597:Amino Acids, Branched-Chain; D011506:Proteins
keywords: Halophile; Halotolerant protein; Molecular evolution; Protein stability; Protein structure; Salt adaptation