Figure 9

Thermostable group II intron reverse transcriptase (RT) fusion proteins. High-level expression of thermostable group II intron RTs that remain soluble when purified free of bound RNAs is achieved by expressing the RT as a fusion protein with a solubility tag, such as MalE or NusA, linked to the N-terminus of the RT via a non-cleavable rigid linker [10]. In these examples, the rigid linker consists of five alanine residues and the MalE and NusA tags are modified (MalE, charged amino acids changed to alanines (italics); NusA, two C-terminal amino acids deleted) to reduce conformational flexibility at the fusion junction and achieve an optimal spacing between the solubility tag and the group II intron RT [10].