Abstract
To probe the structural elements that contribute to the functional asymmetries of the two ubiquinone10 binding pockets in the reaction center of Rhodobacter capsulatus, we targeted the L212Glu–L213Asp (near QB) and the M246Ala-M247Ala (near QA) pairs of symmetry-related residues for site-specific mutagenesis. We have constructed site-specific mutants that eliminate the sequence differences at these positions (L212Glu–L213Asp→Ala-Ala or M246Ala–M247Ala→Glu-Asp), and have reversed that asymmetry by constructing a quadruple-mutant strain, ‘RQ’ (L212Glu–L213Asp-M246Ala–M247Ala→Ala-Ala-Gl u-Asp). The mutations were designed to change the charge distribution in the quinone-binding region of the reaction center; none of the strains is capable of photosynthetic growth. In photocompetent phenotypic revertants of the RQ strain, second-site mutations which affect QB function are coupled to mutations in the QA site which restore an Ala or substitute a Tyr at the M247 site; one strain carries an additional Met→Leu substitution at M260 near QA. All of the RQ revertants retain the engineered M246Ala→Glu mutation in the QA site as well as the L212Ala–L213Ala mutations in the QB site. Kinetic characterization of the RQ revertants will give us an idea of what structural and functional elements are important for restoring efficiency to electron and proton transfer pathways in the RQ RC, which is far from native. To date, these preliminary results underscore the importance of an asymmetric distribution of polar amino acids in the quinone binding pockets and its influence on the functional properties of the reaction center.
Similar content being viewed by others
References
Beroza P, Fredkin DR, Okamura MY and Feher G (1995) Electrostatic calculations of amino acid titration and electron transfer, \({\text{Q}}_{\text{A}}^ - \)QB→QA \({\text{Q}}_{\text{B}}^ - \), in the reaction center. Biophys J 68: 2233–2250
Bylina EJ, Ismail S and Youvan DC (1986) Plasmid pU29, a vehicle for mutagenesis of the photosynthetic puf operon in Rhodopseudomonas capsulata. Plasmid 16: 175–181
Bylina EJ, Jovine RVM and Youvan DC (1989) A genetic system for rapidly assessing herbicides that compete for the quinone binding site of photosynthetic reaction centers. Biotechnology 7: 69–74
Chang C-H, El-Kabbani O, Tiede DM, Norris JR and Schiffer M (1991) The structure of the membrane-bound reaction center from Rhodobacter sphaeroides. Biochemistry 30: 5352–5360
Deisenhofer J, Epp O, Miki R, Huber R and Michel H (1985) Structure of the protein subunits in the photosynthetic reaction center from Rps viridis at 3 Å resolution. Nature 318: 618–624
DiMagno TJ, Laible PD, Reddy NR, Small GJ, Norris JR, Schiffer M and Hanson DK. Protein-chromophore interactions: Spectral shifts report the consequences of mutations in the bacterial photosynthetic reaction center. Spectrochimica Acta A, in press.
Ermler U, Michel H and Schiffer M (1994) Structure and function of the photosynthetic reaction center from Rhodobacter sphaeroides. J Bioenerg Biomemb 26: 5–15
Hanson DK, Nance SL and Schiffer M (1992a) Second-site mutation at M43 (Asn→Asp) compensates for the loss of two acidic residues in the QB site of the reaction center. Photosynth Res 32: 147–153
Hanson DK, Baciou L, Tiede DM, Nance SL, Schiffer M and Sebban P (1992b) In bacterial reaction centers protons can diffuse to the secondary quinone by alternative pathways. Biochim Biophys Acta 1102: 260–265
Hanson DK, Tiede DM, Nance SL, Chang C-H and Schiffer M (1993) Site-specific and compensatory mutations imply unexpected pathways for proton delivery to the QB binding site of the photosynthetic reaction center. Proc Natl Acad Sci USA 90: 8929–8933
Hienerwadel R, Grzybek S, Fogel C, Kreutz W, Okamura MY, Paddock ML, Breton J, Nabedryk E and Mäntele W (1995) Protonation of Glu L212 following \({\text{Q}}_{\text{B}}^ - \) formation in the photosynthetic reaction center of Rhodobacter sphaeroides: Evidence from time-resolved infrared spectroscopy. Biochemistry 34: 2832–2843
Laible PD, Zhang Y, Morris AL, Snyder SW, Ainsworth C, Green-field SR, Wasielewski MR, Parot P, Schoepp B, Schiffer M, Hanson DK and Thurnauer MC (1997) Spectroscopic characterization of quinone-site mutants of the bacterial photosynthetic reaction center. Photosynth Res 52: 93–103
Lancaster CRD, Michel B, Honig B and Gunner MR (1996) Calculated coupling of electron and proton transfer in the photosynthetic reaction center of Rhodopseudomonas viridis. Biophys J 70: 2469–2492
Maróti P, Hanson DK, Baciou L, Schiffer M and Sebban P (1994) Proton conduction within the reaction centers of Rhodobacter capsulatus: The electrostatic role of the protein. Proc Natl Acad Sci USA 91: 5617–5621
Maróti P, Hanson DK, Schiffer M and Sebban P (1995) Long-range electrostatic interaction in the bacterial photosynthetic reaction centre. Nature Structural Biology 2: 1057–1059
Miksovska J, Maróti P, Tandori J, Schiffer M, Hanson DK and Sebban P (1996) Distant electrostatic interactions modulate the free energy level of \({\text{Q}}_{\text{A}}^ - \) in the photosynthetic reaction center. Biochemistry 35: 15411–15417
Miksovska J, Kálmán L, Schiffer M, Maróti P, Sebban P and Hanson DK (1997) In bacterial reaction centers rapid delivery of the second proton to QB can be achieved in the absence of L212Glu. Biochemistry 36: 12216–12226
Nabedryk E, Breton J, Hienerwadel R, Fogel C, Mäntele W, Paddock ML and Okamura MY (1995) Fourier transform infrared difference spectroscopy of secondary quinone acceptor photoreduction in proton transfer mutants of Rhodobacter sphaeroides. Biochemistry 34: 14722–14732
Paddock ML, Rongey SH, Feher G and Okamura MY (1989) Pathway of proton transfer in bacterial reaction centers: Replacement of glutamic acid 212 in the L subunit by glutamine inhibits quinone (secondary acceptor) turnover. Proc Natl Acad Sci USA 86: 6602–6606
Schiffer M, Chan C-K, Chang C-H, DiMagno TJ, Fleming GR, Nance S, Norris J, Snyder S, Thurnauer M, Tiede DM and Hanson DK (1992) Study of reaction center function by analysis of the effects of site-specific and compensatory mutations. In: Breton J and Verméglio A (eds) The Photosynthetic Bacterial Reaction Center II, pp 351–361. Plenum Press, New York
Sebban P, Maróti P and Hanson DK (1995a) Electron and proton transfer to the quinones in bacterial photosynthetic reaction centers: Insight from combined approaches of molecular genetics and biophysics. Biochimie 77: 677–694
Sebban P, Maróti P, Schiffer M and Hanson DK (1995b) Electrostatic dominoes: Long distance propagation of mutational effects in photosynthetic reaction centers of Rhodobacter capsulatus. Biochemistry 34: 8390–8397
Takahashi E, Wraight CA (1992) Proton and electron transfer in the acceptor quinone complex of Rb. sphaeroides: Characterization of site-directed mutants of the two ionizable residues, GluL212 and Asp L213, in the QB binding site. Biochemistry 31: 855–866
Valerio-Lepiniec M, Delcroix JD, Schiffer M, Hanson DK and Sebban P (1997) A native electrostatic environment near QB is not sufficient to ensure rapid proton delivery in photosynthetic reaction centers. FEBS Lett 407: 159–163
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hanson, D.K., Schiffer, M. Symmetry-related mutants in the quinone binding sites of the bacterial reaction center – the effects of changes in charge distribution. Photosynthesis Research 55, 275–280 (1998). https://doi.org/10.1023/A:1005901510444
Issue Date:
DOI: https://doi.org/10.1023/A:1005901510444