Psychrophilic elongation factor Tu from the Antarctic Moraxella sp. Tac II 25: biochemical characterization and cloning of the encoding gene

• Main Authors: MASULLO, Mariorosario, ARCARI P., DE PAOLA B., PARMEGGIANI A., BOCCHINI V.
• Other Authors: Masullo, Mariorosario, Arcari, P., DE PAOLA, B., Parmeggiani, A., Bocchini, V.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2000
• Subjects: Antarctic; Tac; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/11367/18056

The elongation factor Tu was isolated from a psychrophilic eubacterial Antarctic Moraxella strain (MoEF-Tu) and its molecular and functional properties were determined. It catalyzed the synthesis of poly(Phe) and bound specifically guanine nucleotides with an affinity for GDP about 12-fold higher than that for GTP. The affinity toward guanine nucleotides was lower than that of other eubacterial EF- Tu. The intrinsic GTPase activity of MoEF-Tu was hardly detectable but was accelerated by 2 orders of magnitude in the presence of the antibiotic kirromycin (GTPasek). Such a property resembled Escherichia coli EF-Tu (EcEF-Tu) even though the affinity of MoEF-Tu for the antibiotic was lower. MoEF-Tu showed a thermophilicity higher than that of EcEF-Tu; its temperature for half-denaturation was 44 °C. The MoEF- Tu encoding gene corresponding to E. coli tufA was cloned and sequenced. The translated protein had a calculated molecular weight of 43 288 and contained the GTP-binding sequence motifs. Concerning its primary structure, MoEF-Tu showed sequence identity with E. coli and Thermus thermophilus EF-Tu equal to 84% and 74%, respectively, while the identity with EF-1R from the archaeon Sulfolobus solfataricus was equal to 32%.