Abstract
The Zn-BChl-containing reaction center (RC) produced in a bchD (magnesium chelatase) mutant of Rhodobacter sphaeroides assembles with six Zn-bacteriochlorophylls (Zn-BChls) in place of four Mg-containing bacteriochlorophylls (BChls) and two bacteriopheophytins (BPhes). This protein presents unique opportunities for studying biological electron transfer, as Zn-containing chlorins can exist in 4-, 5-, and (theoretically) 6-coordinate states within the RC. In this paper, the electron transfer perturbations attributed exclusively to coordination state effects are separated from those attributed to the presence, absence, or type of metal in the bacteriochlorin at the HA pocket of the RC. The presence of a 4-coordinate Zn 2 + ion in the HA bacteriochlorin instead of BPhe results in a small decrease in the rates of the P* → P+H A- → P+QA- electron transfer, and the charge separation yield is not greatly perturbed; however coordination of the Zn2 + by a fifth ligand provided by a histidine residue results in a larger rate decrease and yield loss. We also report the first crystal structure of a Zn-BChl-containing RC, confirming that the H A Zn-BChl was either 4- or 5-coordinate in the two types of Zn-BChl-containing RCs studied here. Interestingly, a large degree of disorder, in combination with a relatively weak anomalous difference electron density was found in the HB pocket. These data, in combination with spectroscopic results, indicate partial occupancy of this binding pocket. These findings provide insights into the use of BPhe as the bacteriochlorin pigment of choice at HA in both BChl- and Zn-BChl-containing RCs found in nature.
Original language | English (US) |
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Pages (from-to) | 366-374 |
Number of pages | 9 |
Journal | Biochimica et Biophysica Acta - Bioenergetics |
Volume | 1837 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2014 |
Keywords
- Bacteriochlorophyll
- Bacteriopheophytin
- Electron transfer
- Reaction center
- Rhodobacter sphaeroides
- Spectroscopy
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Cell Biology
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Dive into the research topics of 'Structural and kinetic properties of Rhodobacter sphaeroides photosynthetic reaction centers containing exclusively Zn-coordinated bacteriochlorophyll as bacteriochlorin cofactors'. Together they form a unique fingerprint.Datasets
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Zinc Substituted Reaction Center of the Rhodobacter sphaeroides
Saer, R. G. (Contributor), Pan, J. (Contributor), Hardjasa, A. (Contributor), Lin, S. (Contributor), Rosell, F. (Contributor), Mauk, A. G. (Contributor), Woodbury, N. (Contributor), Murphy, M. E. P. (Contributor) & Beatty, J. T. (Contributor), Protein Data Bank (PDB), Feb 5 2014
DOI: 10.2210/pdb4N7K, https://www.wwpdb.org/pdb?id=pdb_00004n7k
Dataset
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Zinc Substituted Reaction Center M(L214H) Variant of Rhodobacter sphaeroides
Saer, R. G. (Contributor), Pan, J. (Contributor), Hardjasa, A. (Contributor), Lin, S. (Contributor), Rosell, F. (Contributor), Mauk, A. G. (Contributor), Woodbury, N. (Contributor), Murphy, M. E. P. (Contributor) & Beatty, J. T. (Contributor), Protein Data Bank (PDB), Jan 22 2014
DOI: 10.2210/pdb4N7L, https://www.wwpdb.org/pdb?id=pdb_00004n7l
Dataset