Diverse sequences are functional at the C-terminus of the E. coli periplasmic chaperone SurA.

摘要: SurA is a major periplasmic molecular chaperone in Escherichia coli and has been shown to assist the biogenesis of several outer membrane proteins. The C-terminal fragment folds into short β-strand, which forms small three-stranded anti-parallel β-sheet module with N-terminal β-hairpin. We found that length fragment, rather than its exact amino acid composition, had big impact on function. To investigate determinant factor sequence, we created library constructs randomized last 10 residues. screened randomly analyzed 19 displayed activity. C-termini these shared little sequence similarity, except β-strand-forming residues were preferentially enriched. Three expressed purified for structural characterization. Circular dichroism fluorescence spectroscopy analyses revealed their structures similar structure wild-type SurA. Our results suggest scaffolding purpose proteins may tolerate various sequences provided certain general requirements such as hydrophobicity secondary propensity are satisfied. Furthermore, tolerance at C-terminus indicates this area not likely be involved substrate binding.