4n7k

Zinc Substituted Reaction Center of the Rhodobacter sphaeroides

spinqualitylabelsall models 4n7k, resolution 2.85Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4n7k is a 3 chain structure with sequence from Cereibacter sphaeroides. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: 2GO, CDL, FE, GGD, GOL, HTO, LDA, PC1, PO4, SPO, U10 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function RCEH_CERSP The reaction center is a membrane-bound complex that mediates the initial photochemical event in the electron transfer process of photosynthesis. Publication Abstract from PubMed 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 Zn2+ ion in the HA bacteriochlorin instead of BPhe results in a small decrease in the rates of the P*-->P+HA--->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 HA 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. Structural and kinetic properties of Rhodobacter sphaeroides photosynthetic reaction centers containing exclusively Zn-coordinated bacteriochlorophyll as bacteriochlorin cofactors.,Saer RG, Pan J, Hardjasa A, Lin S, Rosell F, Mauk AG, Woodbury NW, Murphy ME, Beatty JT Biochim Biophys Acta. 2013 Dec 5;1837(3):366-374. doi:, 10.1016/j.bbabio.2013.11.015. PMID:24316146 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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