Fast events in protein folding initiated by nanosecond laser photolysis (original) (raw)

Abstract

Initiation of protein folding by light can dramatically improve the time resolution of kinetic studies. Here we present an example of an optically triggered folding reaction by using nanosecond photodissociation of the heme-carbon monoxide complex of reduced cytochrome c. The optical trigger is based on the observation that under destabilizing conditions cytochrome c can be unfolded by preferential binding of carbon monoxide to the covalently attached heme group in the unfolded state. Photodissociation of the carbon monoxide thus triggers the folding reaction. We used time-resolved absorption spectroscopy to monitor binding at the heme. Before folding begins we observe transient binding of both nonnative and native ligands from the unfolded polypeptide on a microsecond time scale. Kinetic modeling suggests that the intramolecular binding of methionine-65 and -80 is faster than that of histidine-26 and -33, even though the histidines are closer to the heme. This optical trigger should provide a powerful method for studying chain collapse and secondary structure formation in cytochrome c without any limitations in time resolution.

11860

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Anfinrud P. A., Han C., Hochstrasser R. M. Direct observations of ligand dynamics in hemoglobin by subpicosecond infrared spectroscopy. Proc Natl Acad Sci U S A. 1989 Nov;86(21):8387–8391. doi: 10.1073/pnas.86.21.8387. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Ansari A., Jones C. M., Henry E. R., Hofrichter J., Eaton W. A. Photoselection in polarized photolysis experiments on heme proteins. Biophys J. 1993 Mar;64(3):852–868. doi: 10.1016/S0006-3495(93)81446-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Ansari A., Jones C. M., Henry E. R., Hofrichter J., Eaton W. A. The role of solvent viscosity in the dynamics of protein conformational changes. Science. 1992 Jun 26;256(5065):1796–1798. doi: 10.1126/science.1615323. [DOI] [PubMed] [Google Scholar]
  4. Brautigan D. L., Ferguson-Miller S., Margoliash E. Mitochondrial cytochrome c: preparation and activity of native and chemically modified cytochromes c. Methods Enzymol. 1978;53:128–164. doi: 10.1016/s0076-6879(78)53021-8. [DOI] [PubMed] [Google Scholar]
  5. Brems D. N., Stellwagen E. Manipulation of the observed kinetic phases in the refolding of denatured ferricytochromes c. J Biol Chem. 1983 Mar 25;258(6):3655–3660. [PubMed] [Google Scholar]
  6. Chernoff D. A., Hochstrasser R. M., Steele A. W. Geminate recombination of O2 and hemoglobin. Proc Natl Acad Sci U S A. 1980 Oct;77(10):5606–5610. doi: 10.1073/pnas.77.10.5606. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Creighton T. E. Protein folding. Biochem J. 1990 Aug 15;270(1):1–16. doi: 10.1042/bj2700001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Dill K. A., Fiebig K. M., Chan H. S. Cooperativity in protein-folding kinetics. Proc Natl Acad Sci U S A. 1993 Mar 1;90(5):1942–1946. doi: 10.1073/pnas.90.5.1942. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Elöve G. A., Chaffotte A. F., Roder H., Goldberg M. E. Early steps in cytochrome c folding probed by time-resolved circular dichroism and fluorescence spectroscopy. Biochemistry. 1992 Aug 4;31(30):6876–6883. doi: 10.1021/bi00145a003. [DOI] [PubMed] [Google Scholar]
  10. Fisher W. R., Taniuchi H., Anfinsen C. B. On the role of heme in the formation of the structure of cytochrome c. J Biol Chem. 1973 May 10;248(9):3188–3195. [PubMed] [Google Scholar]
  11. Frauenfelder H., Wolynes P. G. Rate theories and puzzles of hemeprotein kinetics. Science. 1985 Jul 26;229(4711):337–345. doi: 10.1126/science.4012322. [DOI] [PubMed] [Google Scholar]
  12. Greene B. I., Hochstrasser R. M., Weisman R. B., Eaton W. A. Spectroscopic studies of oxy- and carbonmonoxyhemoglobin after pulsed optical excitation. Proc Natl Acad Sci U S A. 1978 Nov;75(11):5255–5259. doi: 10.1073/pnas.75.11.5255. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Hofrichter J., Henry E. R., Szabo A., Murray L. P., Ansari A., Jones C. M., Coletta M., Falcioni G., Brunori M., Eaton W. A. Dynamics of the quaternary conformational change in trout hemoglobin. Biochemistry. 1991 Jul 2;30(26):6583–6598. doi: 10.1021/bi00240a031. [DOI] [PubMed] [Google Scholar]
  14. Hofrichter J., Sommer J. H., Henry E. R., Eaton W. A. Nanosecond absorption spectroscopy of hemoglobin: elementary processes in kinetic cooperativity. Proc Natl Acad Sci U S A. 1983 Apr;80(8):2235–2239. doi: 10.1073/pnas.80.8.2235. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Jones C. M., Ansari A., Henry E. R., Christoph G. W., Hofrichter J., Eaton W. A. Speed of intersubunit communication in proteins. Biochemistry. 1992 Jul 28;31(29):6692–6702. doi: 10.1021/bi00144a008. [DOI] [PubMed] [Google Scholar]
  16. Kim P. S., Baldwin R. L. Intermediates in the folding reactions of small proteins. Annu Rev Biochem. 1990;59:631–660. doi: 10.1146/annurev.bi.59.070190.003215. [DOI] [PubMed] [Google Scholar]
  17. Kuwajima K. The molten globule state as a clue for understanding the folding and cooperativity of globular-protein structure. Proteins. 1989;6(2):87–103. doi: 10.1002/prot.340060202. [DOI] [PubMed] [Google Scholar]
  18. Martin J. L., Migus A., Poyart C., Lecarpentier Y., Astier R., Antonetti A. Femtosecond photolysis of CO-ligated protoheme and hemoproteins: appearance of deoxy species with a 350-fsec time constant. Proc Natl Acad Sci U S A. 1983 Jan;80(1):173–177. doi: 10.1073/pnas.80.1.173. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Matthews C. R. Pathways of protein folding. Annu Rev Biochem. 1993;62:653–683. doi: 10.1146/annurev.bi.62.070193.003253. [DOI] [PubMed] [Google Scholar]
  20. Roder H., Elöve G. A., Englander S. W. Structural characterization of folding intermediates in cytochrome c by H-exchange labelling and proton NMR. Nature. 1988 Oct 20;335(6192):700–704. doi: 10.1038/335700a0. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Tsong T. Y. The Trp-59 fluorescence of ferricytochrome c as a sensitive measure of the over-all protein conformation. J Biol Chem. 1974 Mar 25;249(6):1988–1990. [PubMed] [Google Scholar]
  22. Vanderkooi J. M., Erecińska M. Cytochrome c interaction with membranes. Absorption and emission spectra and binding characteristics of iron-free cytochrome c. Eur J Biochem. 1975 Dec 1;60(1):199–207. doi: 10.1111/j.1432-1033.1975.tb20992.x. [DOI] [PubMed] [Google Scholar]