In Situ, Protein-Mediated Generation of a Photochemically Active Chlorophyll Analogue in a Mutant Bacterial Photosynthetic Reaction Center
| Autor: | Gregory A. Tira, Philip D. Laible, Christine Kirmaier, Dewey Holten, Nikki Cecil M. Magdaong, Kaitlyn M. Faries, Haijun Liu, Jonathan S. Lindsey, Deborah K. Hanson, James C. Buhrmaster |
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| Rok vydání: | 2021 |
| Předmět: |
Chlorophyll
Photosynthetic reaction centre chemistry.chemical_classification Cofactor binding biology Stereochemistry Photosynthetic Reaction Center Complex Proteins Rhodobacter sphaeroides Photochemical Processes biology.organism_classification Biochemistry Cofactor Amino acid chemistry.chemical_compound Electron transfer chemistry Mutation Chlorin biology.protein Oxidation-Reduction |
| Zdroj: | Biochemistry. 60:1260-1275 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/acs.biochem.1c00137 |
| Popis: | All possible natural amino acids have been substituted for the native LeuL185 positioned near the B-side bacteriopheophytin (HB) in the bacterial reaction center (RC) from Rhodobacter sphaeroides. Additional mutations that enhance electron transfer to the normally inactive B-side cofactors are present. Approximately half of the isolated RCs with Glu at L185 contain a magnesium chlorin (CB) in place of HB. The chlorin is not the common BChl a oxidation product 3-desvinyl-3-acetyl chlorophyll a with a C-C bond in ring D and a C═C bond in ring B but has properties consistent with reversal of these bond orders, giving 17,18-didehydro BChl a. In such RCs, charge-separated state P+CB- forms in ∼5% yield. The other half of the GluL185-containing RCs have a bacteriochlorophyll a (BChl a) denoted βB in place of HB. Residues His, Asp, Asn, and Gln at L185 yield RCs with ≥85% βB in the HB site, while most other amino acids result in RCs that retain HB (≥95%). To the best of our knowledge, neither bacterial RCs that harbor five BChl a molecules and one chlorophyll analogue nor those with six BChl a molecules have been reported previously. The finding that altering the local environment within a cofactor binding site of a transmembrane complex leads to in situ generation of a photoactive chlorin with an unusual ring oxidation pattern suggests new strategies for amino acid control over pigment type at specific sites in photosynthetic proteins. |
| Databáze: | OpenAIRE |
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