Single-molecule spectroscopy reveals that individual low-light lh2 complexes from Rhodopseudomonas palustris 2.1.6. have a heterogeneous polypeptide composition

Brotosudarmo, T.H.P., Kunz, R., Bohm, P., Gardiner, A.T., Moulisova, V. , Cogdell, R.J. and Kohler, J. (2009) Single-molecule spectroscopy reveals that individual low-light lh2 complexes from Rhodopseudomonas palustris 2.1.6. have a heterogeneous polypeptide composition. Biophysical Journal, 97(5), pp. 1491-1500. (doi:10.1016/j.bpj.2009.06.034) (PMID:19720038) (PMCID:PMC2749768)

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Abstract

Rhodopseudomonas palustris belongs to the group of purple bacteria that have the ability to produce LH2 complexes with unusual absorption spectra when they are grown at low-light intensity. This ability is often related to the presence of multiple genes encoding the antenna apoproteins. Here we report, for the first time to our knowledge, direct evidence that individual low-light LH2 complexes have a heterogeneous [alpha][beta]-apoprotein composition that modulates the site energies of Bchl a molecules, producing absorption bands at 800, 820, and 850 nm. The arrangement of the Bchl a molecules in the "tightly coupled ring" can be modeled by nine [alpha][beta]-Bchls dimers, such that the Bchls bound to six [alpha][beta]-pairs have B820-like site energies and the remaining Bchl a molecules have B850-like site energies. Furthermore, the experimental data can only be satisfactorily modeled when these six [alpha][beta]-pairs with B820 Bchl a molecules are distributed such that the symmetry of the assembly is reduced to C3. It is also clear from the measured single-molecule spectra that the energies of the electronically excited states in the mixed B820/850 ring are mainly influenced by diagonal disorder

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Moulisova, Dr Vladimira and Cogdell, Professor Richard
Authors: Brotosudarmo, T.H.P., Kunz, R., Bohm, P., Gardiner, A.T., Moulisova, V., Cogdell, R.J., and Kohler, J.
Subjects:Q Science > QH Natural history > QH301 Biology
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Biophysical Journal
Journal Abbr.:Biophys J.
ISSN:0006-3495
ISSN (Online):1542-0086

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
303032The structure and function of purple bacterial antenna complexesRichard CogdellBiotechnology and Biological Sciences Research Council (BBSRC)BB/D000610/1Institute of Molecular Cell and Systems Biology