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Cover Picture: Learning from Directed Evolution: Thermus aquaticus DNA Polymerase Mutants with Translesion Synthesis Activity (ChemBioChem 10/2011)
The cover picture shows a crystal structure of KenTaq DNA polymerase bypassing an abasic site analogue. Abasic sites are the most frequent lesions to arise under physiological conditions and represent a strong block for replicative DNA polymerases. However, nature offers a vast arsenal of specialized DNA polymerases that have evolved for translesion bypass. On p. 1574 ff., A. Marx et al. show how, starting from DNA polymerase that is incompetent in translesion synthesis, they substituted two nonpolar amino acid side chains with two cationic side chains to give a DNA polymerase mutant with enhanced translesion synthesis capability. The mutant shows expanded positively charged surface potential areas, which are also found in naturally evolved translesion DNA polymerases. The results underscore the impact of charge on the proficiency of naturally evolved translesion DNA polymerases.