John Golbeck

Professor of Biochemistry and Biophysics
Professor of Chemistry

310 South Frear Laboratory, University Park, PA 16802
Phone: (814) 865-1163
Fax: (814) 863-7024
E-mail: jhg5@psu.edu

B.S. in Chemistry from Valparaiso University
Ph.D. in Chemistry from Indiana University

Golbeck Lab Web Site

We have developed a protocol to differentiate flash-induced absorption changes of the primary donor, P840/P840+, from the decay of 3Bchl a in the Fenna-Matthews-Olson (FMO) protein in Chlorobium vibrioforme and we showed that the 70-ms component corresponds to the decay of 3Bchl a in the FMO protein and that the 1.6-ms component corresponds to P840/P840+. A redox titration of FA and FB in isolated PscB from Chlorobium tepidum indicates that both clusters have identical Em values of –450 mV. PscB is therefore similar to PsaC in PS I in that the redox potentials of the FeS clusters become differentiated when the protein is bound to the reaction center. A quantitative analysis of microwave power saturation profiles showed that the P1/2 of P840+ and the P1/2 of P840+ FA- FB- were similar to the P1/2 of P700+ and the P1/2 of P700+ FA- FB- in Photosystem I. Thus, the geometry of the terminal FeS clusters with respect to the primary donor is likely to be similar in C. tepidum and Photosystem I (Figure 2.3.1.). The chlorosome envelope FeS proteins CsmI and CsmJ were expressed in Escherichia coli, and a redox titration was carried out. The Em for CsmI was –201 mV the Em for CsmJ was +92 mV. A comparable redox titration carried out on wild-type chlorosomes showed Em values of –346 mV and +90 mV. The difference may be due to the occurrence of CsmI and CsmJ heterodimers in the chlorosome envelope.

Figure 2.3.1. Hypothetical energetic diagram of C. tepidum RC showing a proposed larger free energy difference between A1 and FX than in Photosystem I.

Kjaer, B., Jung, Y. S., Yu, L. A., Golbeck, J. H., and Scheller, H. V. (1994) Iron-sulfur centers in the photosynthetic reaction center complex from Chlorobium vibrioforme. differences from and similarities to the iron-sulfur centers in Photosystem I, Photosynth Res 41, 105-114.

Scott, M. P., Kjoer, B., Scheller, H. V., and Golbeck, J. H. (1997) Redox titration of two [4Fe-4S] clusters in the photosynthetic reaction center from the anaerobic green sulfur bacterium Chlorobium vibrioforme, Eur J Biochem 244, 454-461.

Vassiliev, I. R., Ronan, M. T., Hauska, G., and Golbeck, J. H. (2000) The bound electron acceptors in green sulfur bacteria: resolution of the g-tensor for the FX iron-sulfur cluster in Chlorobium tepidum, Biophys J 78, 3160-9.

Vassiliev, I. R., Kjaer, B., Schorner, G. L., Scheller, H. V., and Golbeck, J. H. (2001) Photoinduced transient absorbance spectra of P840/P840+ and the FMO protein in reaction centers of Chlorobium vibrioforme, Biophys J 81, 382-93.

Johnson, T. W., Li, H., Frigaard, N.-U., Bryant, D. A., and Golbeck, J. H. (2004) Redox titration of the [2Fe-2S] clusters in the CsmI, CsmJ, and CsmX proteins in the chlorosome envelope of wild type and mutant Chlorobium tepidum, Biochem. (in review).