1yf6
From Proteopedia
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'''Structure of a quintuple mutant of photosynthetic reaction center from rhodobacter sphaeroides''' | '''Structure of a quintuple mutant of photosynthetic reaction center from rhodobacter sphaeroides''' | ||
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[[Category: Paddock, M L.]] | [[Category: Paddock, M L.]] | ||
[[Category: Xu, Q.]] | [[Category: Xu, Q.]] | ||
| - | [[Category: | + | [[Category: Bacterial photosynthesis]] |
| - | [[Category: | + | [[Category: Gated electron transfer]] |
| - | [[Category: | + | [[Category: Integral membrane protein]] |
| - | [[Category: | + | [[Category: Quinone movement]] |
| - | [[Category: | + | [[Category: Rhodobacter sphaeroide]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 16:14:44 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 13:14, 3 May 2008
Structure of a quintuple mutant of photosynthetic reaction center from rhodobacter sphaeroides
Overview
The photosynthetic reaction center (RC) from purple bacteria converts light into chemical energy. Although the RC shows two nearly structurally symmetric branches, A and B, light-induced electron transfer in the native RC occurs almost exclusively along the A-branch to a primary quinone electron acceptor Q(A). Subsequent electron and proton transfer to a mobile quinone molecule Q(B) converts it to a quinol, Q(B)H(2). We report the construction and characterization of a series of mutants in Rhodobacter sphaeroides designed to reduce Q(B) via the B-branch. The quantum efficiency to Q(B) via the B-branch Phi(B) ranged from 0.4% in an RC containing the single mutation Ala-M260 --> Trp to 5% in a quintuple mutant which includes in addition three mutations to inhibit transfer along the A-branch (Gly-M203 --> Asp, Tyr-M210 --> Phe, Leu-M214 --> His) and one to promote transfer along the B-branch (Phe-L181 --> Tyr). Comparing the value of 0.4% for Phi(B) obtained in the AW(M260) mutant, which lacks Q(A), to the 100% quantum efficiency for Phi(A) along the A-branch in the native RC, we obtain a ratio for A-branch to B-branch electron transfer of 250:1. We determined the structure of the most effective (quintuple) mutant RC at 2.25 A (R-factor = 19.6%). The Q(A) site did not contain a quinone but was occupied by the side chain of Trp-M260 and a Cl(-). In this structure a nonfunctional quinone was found to occupy a new site near M258 and M268. The implications of this work to trap intermediate states are discussed.
About this Structure
1YF6 is a Protein complex structure of sequences from Rhodobacter sphaeroides. Full crystallographic information is available from OCA.
Reference
Quinone (QB) reduction by B-branch electron transfer in mutant bacterial reaction centers from Rhodobacter sphaeroides: quantum efficiency and X-ray structure., Paddock ML, Chang C, Xu Q, Abresch EC, Axelrod HL, Feher G, Okamura MY, Biochemistry. 2005 May 10;44(18):6920-8. PMID:15865437 Page seeded by OCA on Sat May 3 16:14:44 2008
