tailieunhanh - Báo cáo khoa học: Fish and molluscan metallothioneins A structural and functional comparison

Metallothioneins (MTs) are noncatalytic peptides involved in storage of essential ions, detoxification of nonessential metals, and scavenging of oxyradicals. They exhibit an unusual primary sequence and unique 3D arrangement. Whereas vertebrate MTs are characterized by the well-known dumbbell shape, with abdomain that binds three bivalent metal ions and anadomain that binds four ions, molluscan MT structure is still poorly understood. | iFEBS Journal Fish and molluscan metallothioneins A structural and functional comparison Laura Vergani1 Myriam Grattarola1 Cristina Borghi2 Francesco Dondero3 and Aldo Viarengo3 4 1 Department of BiophysicalSciences and Technologies M. O. University of Genova Italy 2 Department of Biology University of Genova Italy 3 Department of Environmental Life Science University of Piemonte Orientale Alessandria Italy 4 Center on Biology and Chemistry of Trace Metals University of Genova Italy Keywords absorbance spectroscopy circular dichroism metal release structure function relationship thermal stability Correspondence L. Vergani Department of Biophysical Sciences and Technologies M. O. University of Genova Corso Europa 30 16132 Genova Italy Fax 39 010 3538346 Tel 39 010 3538404 E-mail Received 6 July 2005 revised 14 September 2005 accepted 26 September 2005 doi Metallothioneins MTs are noncatalytic peptides involved in storage of essential ions detoxification of nonessential metals and scavenging of oxyradicals. They exhibit an unusual primary sequence and unique 3D arrangement. Whereas vertebrate MTs are characterized by the well-known dumbbell shape with a b domain that binds three bivalent metal ions and an a domain that binds four ions molluscan MT structure is still poorly understood. For this reason we compared two MTs from aquatic organisms that differ markedly in primary structure MT 10 from the invertebrate Mytilus galloprovincialis and MT A from Oncorhyncus mykiss. Both proteins were overexpressed in Escherichia coli as glutathione S-transferase fusion proteins and the MT moiety was recovered after protease cleavage. The MTs were analyzed by gel electrophoresis and tested for their differential reactivity with alkylating and reducing agents. Although they show an identical cadmium content and a similar metal-binding ability spectro-polarimetric analysis disclosed significant differences in the Cd7-MT .