Crystallographic studies of the Antarctic alkaline phosphatase TAB5

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Project leader: Professor Edward Hough


Alkaline phosphatases (APs) are widely used in molecular biology for the removal of 5` phosphate groups from DNA and RNA. These processes have to be terminated after a suitable time to avoid unwanted further de-phosphorylation. Although bacterial enzymes show the highest catalytic activity they have to be removed at the end of the reaction by proteolytic digestion at 75C. For this reason the enzymes from cold adapted species have recently found wide applications. The enzyme from the arctic shrimp Pandalus borealis (Biotec Pharmacon,Tromsø) is particularly suitable since it can be deactivated by a short treatment at 65C. The structure was solved by Maaike de Backer.
Through collaboration with Professor Vassilis Bouriotis, Division of Applied Biology and Biotechnology, University of Crete, the alkaline phosphatase which his co-workers have isolated, sequenced, cloned and now overexpressed from the cold adapted Antarctic strain TAB54 has been crystallised and the structure is solved.
Structures of APs from E.coli human placenta and shrimp have been reported. These enzymes contain 456, 479, 476, amino acids respectively and show considerable structural similarity. With its 353 amino acids in the active form, TAB5 is considerable smaller than its siblings and may represent a minimal requirement for activity. However sequence comparison and biochemical studies confirm that the enzyme is a classic 2Zn, 1Mg alkaline phosphatase.