Purification of a recombinant human respiratory syncytial virus chimeric glycoprotein using reversed-phase chromatography and protein refolding in guanidine hydrochloride.

FG glycoprotein is a recombinant chimeric protein consisting of the extracellular portions of human respiratory syncytial virus (RSV) F and G glycoproteins. In theory, highly purified FG glycoprotein may be effective as a RSV vaccine. Recombinant FG glycoprotein was expressed using the baculovirus/insect cell system. FG glycoprotein was isolated from cell culture supernatants using S Sepharose ion-exchange chromatography, Cu(2+)-immobilized metal affinity chromatography, preparative reversed-phase high-performance liquid chromatography, denaturation with 6 M guanidine hydrochloride, and protein refolding in Tween 80 detergent. The purified FG glycoprotein was concentrated on a S Sepharose column and exchanged into an appropriate buffer for vaccine formulation. Five batches of FG glycoprotein with protein purity of 92-99% were produced using this purification process. FG glycoprotein produced using reversed-phase chromatography and protein refolding was compared with nondenatured FG glycoprotein using a panel of 14 monoclonal antibodies directed against conformational and linear epitopes on RSV F and G glycoproteins. The results of these studies indicated that refolded FG glycoprotein had the same three-dimensional structure as nondenatured FG glycoprotein.

Site-directed mutagenesis to probe protein folding: evidence that the formation and aggregation of a bovine growth hormone folding intermediate are dissociable processes.

Bovine growth hormone (bGH) forms a stable folding intermediate that aggregates at elevated concentrations (greater than 10 microM). Thermodynamic and kinetic studies have shown that the formation of this bGH folding intermediate and its aggregation are separate processes, implying that selective modifications of bGH can lead to their independent modulation. In addition, a bGH region that includes amino acid residues 109-133 appears to be directly involved in this aggregation process. Human growth hormone (hGH), which is unable to aggregate via this mechanism, differs from the bovine primary sequence at eight positions within this protein region. We have characterized the folding of a bGH analogue that contains the hGH sequence between amino acid residues 109-133 (8H-bGH) at low and high concentrations. The equilibrium folding characteristics of bGH and 8H-bGH are similar when monitored at low protein concentrations (less than or equal to 2 microM). The wild-type and analogue proteins have equivalent denaturation midpoints when equilibrium unfolding is monitored by the use of far-UV circular dichroism, second-derivative UV, or fluorescence. In addition, the enhanced fluorescence that is associated with the formation of the bGH monomeric folding intermediate (Havel, H. A., et al. (1988) Biochim. Biophys. Acta 955, 154-163) is observed for 8H-bGH under similar conditions. In contrast, partial denaturation of 8H-bGH at higher concentrations (greater than 2 microM) leads to significantly less aggregation than is observed for bGH. This result is obtained from near-UV CD spectroscopy, kinetic folding, size-exclusion chromatography, and dynamic light-scattering data.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptide alpha-helicity in aqueous trifluoroethanol: correlations with predicted alpha-helicity and the secondary structure of the corresponding regions of bovine growth hormone.

The relationship between trifluoroethanol (TFE) enhancement of peptide alpha-helicity and protein secondary structure has been studied for a series of 11 peptides which span the complete primary sequence of bovine growth hormone (bGH). Ten of these peptides become increasingly alpha-helical as the solution concentration of TFE is increased. The amount of alpha-helicity developed by these peptides plateaus above 10 mol % TFE and ranges from 0 to 71%. The increased alpha-helicity, as determined by CD, closely correlates with the amount of alpha-helix predicted for eight of the eleven peptides analyzed (r = 0.9). Therefore, for this group of peptides, it appears that this technique can be used as a measure of alpha-helical propensity. Inclusion of the remaining three peptides in this analysis significantly lowers the correlation (r = 0.6). The reduced correspondence between TFE-enhanced and predicted alpha-helicity in this latter subset of peptides may be due to their relatively high hydrophobicity. In addition, the relevance of TFE-enhanced peptide alpha-helicity and the secondary structure of the corresponding protein regions was explored. Although the three peptides which form the largest amount of alpha-helicity in the presence of 10 mol % TFE correspond to alpha-helical regions of the protein, the overall correlation is significantly lower than is observed for the TFE-enhanced and predicted alpha-helicity. These findings suggest that the propensity of specific amino acid sequences for alpha-helix formation influences the amount of alpha-helicity which forms in corresponding protein sequences, but that other factors can modify this structure.