ADENYLATE KINASE FROM SULFOLOBUS-ACIDOCALDARIUS - EXPRESSION IN ESCHERICHIA-COLI AND CHARACTERIZATION BY FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

Adenylate kinase from the extremely thermoacidophilic archaeon Sulfolo bus acidocaldarius has been overexpressed in Escherichia coli. The hig hly purified enzyme was characterized by Fourier transform infrared sp ectroscopy (FTIR). Analysis of FTIR spectra and estimation of secondar y structure revealed a global protein structure similar to that of oth er adenylate kinases. Thermal unfolding of the protein with an estimat ed T-m value near 90 degrees C is irreversible due to protein aggregat ion. The enzyme exhibits long-term stability up to 80 degrees C, which is an excellent adaptation to the physiological growth temperature of 75-80 degrees C. Halfwidths of secondary-structure-sensitive bands an d hydrogen-deuterium exchange experiments revealed that in comparison to adenylate kinase from porcine muscle cytosol the Sulfolobus enzyme is characterized by a significantly more compact and rigid protein cor e structure, which is likely to contribute specifically to the extreme thermostability of the protein. (C) 1996 Academic Press, Inc.