RAS 3min: DHFR 1.7min: His-tagged fusion protein ~24min min
||Netzer WJ, Hartl FU. Recombination of protein domains facilitated by co-translational folding in eukaryotes. Nature. 1997 Jul 24 388(6640):343-9. DOI: 10.1038/41024 p.344 right column 2nd paragraphPubMed ID9237751
||P.344 left column 2nd paragraph: "Here [investigators] tested the hypothesis that sequential folding of domains during synthesis on ribosomes minimizes the error rate of folding for complex proteins. This mechanism would reduce the problem of folding a large polypeptide to that of folding small polypeptide modules. [They] have constructed new composite proteins by joining single-domain proteins with a flexible linker. In vitro refolding of these fusion proteins is inefficient as a result of intramolecular misfolding. In contrast, during eukaryotic translation, the model proteins reach their native state efficiently by sequential and co-translational folding of domains. Remarkably, folding of the same proteins in a bacterial system is post-translational and leads to aggregation. [They] propose that co-translational, domain-wise folding is the basis for the efficient folding of a large number of eukaryotic multidomain proteins."
||P.344 right column 2nd paragraph: "Refolding of Ras and DHFR [dihydrofolate reductase] was analysed at submicromolar protein concentrations where sedimentable aggregates did not form. Mixing the two single-domain proteins in their unfolded states (in trans) had no effect on the yield and rate of refolding (Fig. 2b). The time constants (tau) for folding of the ras and DHFR proteins were 3 and 1.7 min, respectively. (Refolding rates for DHFR and DHFR–His were indistinguishable). However, in the His-tagged fusion protein both Ras and DHFR domains (in cis) refolded concurrently with an 8-fold slower time constant of ~24 min, suggesting that there is intramolecular interference between the Ras and DHFR polypeptides."