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Báo cáo khoa học: The role of evolutionarily conserved hydrophobic contacts in the quaternary structure stability of Escherichia coli serine hydroxymethyltransferase

Pyridoxal 5¢-phosphate-dependent enzymes may be grouped into five struc-tural superfamilies of proteins, corresponding to as many fold types. The fold type I is by far the largest and most investigated group. An important feature of this fold, which is characterized by the presence of two domains, appears to be the existence of three clusters of evolutionarily conserved hydrophobic contacts. | The role of evolutionarily conserved hydrophobic contacts in the quaternary structure stability of Escherichia coli serine hydroxymethyltransferase Rita Florio1 Roberta Chiaraluce1 Valerio Consalvi1 Alessandro Paiardini1 Bruno Catacchio1 2 Francesco Bossa1 3 and Roberto Contestabile1 1 Dipartimento di Scienze Biochimiche A. Rossi Fanelli Sapienza Universita di Roma Italy 2 CNR Istituto di Biologia e Patologia Molecolari Sapienza University di Roma Italy 3 Centro di Eccellenza di Biologia e Medicina Molecolare BEMM Sapienza Universita di Roma Italy Keywords conserved hydrophobic contacts fold type I enzymes pyridoxal phosphate quaternary structure serine hydroxymethyltransferase Correspondence R. Contestabile Dipartimento di Scienze Biochimiche Sapienza Universita di Roma Piazzale Aldo Moro 5 00185 Rome Italy Fax 39 0649 917566 Tel 39 0649 917569 E-mail roberto.contestabile@uniroma1.it Website http w3.uniroma1.it bio_chem sito_biochimica EN index.html Received 18 September 2008 revised 23 October 2008 accepted 27 October 2008 doi 10.1111 j.1742-4658.2008.06761.x Pyridoxal 5 -phosphate-dependent enzymes may be grouped into five structural superfamilies of proteins corresponding to as many fold types. The fold type I is by far the largest and most investigated group. An important feature of this fold which is characterized by the presence of two domains appears to be the existence of three clusters of evolutionarily conserved hydrophobic contacts. Although two of these clusters are located in the central cores of the domains and presumably stabilize their scaffold allowing the correct alignment of the residues involved in cofactor and substrate binding the role of the third cluster is much less evident. A site-directed mutagenesis approach was used to carry out a model study on the importance of the third cluster in the structure of a well characterized member of the fold type I group serine hydroxymethyltransferase from Escherichia coli. The experimental results .