scholarly journals Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9 Å: the structural basis for dimerisation

2021 ◽  
Author(s):  
Pu Qian ◽  
Tristan Ian Croll ◽  
Andrew Hitchcock ◽  
Philip J Jackson ◽  
Jack H Salisbury ◽  
...  

The dimeric reaction centre light-harvesting 1 (RC-LH1) core complex of Rhodobacter sphaeroides converts absorbed light energy to a charge separation, and then it reduces a quinone electron and proton acceptor to a quinol. The angle between the two monomers imposes a bent configuration on the dimer complex, which exerts a major influence on the curvature of the membrane vesicles, known as chromatophores, where the light-driven photosynthetic reactions take place. To investigate the dimerisation interface between two RC-LH1 monomers, we determined the cryogenic electron microscopy structure of the dimeric complex at 2.9 Å resolution. The structure shows that each monomer consists of a central RC partly enclosed by a 14-subunit LH1 ring held in an open state by PufX and protein-Y polypeptides, thus enabling quinones to enter and leave the complex. Two monomers are brought together through N-terminal interactions between PufX polypeptides on the cytoplasmic side of the complex, augmented by two novel transmembrane polypeptides, designated protein-Z, that bind to the outer faces of the two central LH1 β polypeptides. The precise fit at the dimer interface, enabled by PufX and protein-Z, by C-terminal interactions between opposing LH1 αβ subunits, and by a series of interactions with a bound sulfoquinovosyl diacylglycerol lipid, bring together each monomer creating an S-shaped array of 28 bacteriochlorophylls. The seamless join between the two sets of LH1 bacteriochlorophylls provides a path for excitation energy absorbed by one half of the complex to migrate across the dimer interface to the other half.

Author(s):  
Congcong Sun ◽  
Baokui Xu ◽  
Xueyan Liu ◽  
Zhen Zhang ◽  
Zhongliang Su

Enolase is an important enzyme in glycolysis and various biological processes. Its dysfunction is closely associated with diseases. Here, the enolase fromDrosophila melanogaster(DmENO) was purified and crystallized. A crystal of DmENO diffracted to 2.0 Å resolution and belonged to space groupR32. The structure was solved by molecular replacement. Like most enolases, DmENO forms a homodimer with conserved residues in the dimer interface. DmENO possesses an open conformation in this structure and contains conserved elements for catalytic activity. This work provides a structural basis for further functional and evolutionary studies of enolase.


2016 ◽  
Vol 12 ◽  
pp. 854-862 ◽  
Author(s):  
Phil M Pithan ◽  
David Decker ◽  
Manlio Sutero Sardo ◽  
Giampietro Viola ◽  
Heiko Ihmels

Cationic biaryl derivatives were synthesized by Suzuki–Miyaura coupling of 3-bromonaphtho[1,2-b]quinolizinium bromide with arylboronic acids. The resulting cationic biaryl derivatives exhibit pronounced fluorosolvatochromic properties. First photophysical studies in different solvents showed that the emission energy of the biaryl derivatives decreases with increasing solvent polarity. This red-shifted emission in polar solvents is explained by a charge shift (CS) in the excited state and subsequent solvent relaxation. Furthermore, the polarity of protic polar and aprotic polar solvents affects the emission energy to different extent, which indicates a major influence of hydrogen bonding on the stabilization of the ground and excited states.


2015 ◽  
Vol 290 (45) ◽  
pp. 27280-27296 ◽  
Author(s):  
Soumya Mohanty ◽  
Chacko Jobichen ◽  
Vishnu Priyanka Reddy Chichili ◽  
Adrián Velázquez-Campoy ◽  
Boon Chuan Low ◽  
...  

1998 ◽  
Vol 26 (3) ◽  
pp. S209-S209
Author(s):  
Justin P. Ridge ◽  
Matthew G. Goodwin ◽  
Marion van Brederode ◽  
Rienk van Grondelle ◽  
Michael R. Jones

2009 ◽  
Vol 66 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Mads Gabrielsen ◽  
Lisa A. Nagy ◽  
Lawrence J. DeLucas ◽  
Richard J. Cogdell

The second virial coefficient, orBvalue, is a measurement of how well a protein interacts with itself in solution. These interactions can lead to protein crystallization or precipitation, depending on their strength, with a narrow range ofBvalues (the `crystallization slot') being known to promote crystallization. A convenient method of determining theBvalue is by self-interaction chromatography. This paper describes how the light-harvesting complex 1–reaction centre core complex fromAllochromatium vinosumyielded single straight-edged crystals after iterative cycles of self-interaction chromatography and crystallization. This process allowed the rapid screening of small molecules and detergents as crystallization additives. Here, a description is given of how self-interaction chromatography has been utilized to improve the crystallization conditions of a membrane protein.


2019 ◽  
Author(s):  
Zhu Liu ◽  
Xu Dong ◽  
Hua-Wei Yi ◽  
Ju Yang ◽  
Zhou Gong ◽  
...  

ABSTRACTThe interaction between K48-linked ubiquitin (Ub) chain and Rpn13 is important for proteasomal degradation of ubiquitinated substrate proteins. Only the complex structure between the N-terminal domain of Rpn13 (Rpn13NTD) and Ub monomer has been characterized, and it remains unclear how Rpn13 specifically recognizes K48-linked Ub chain. Using single-molecule FRET, here we show that K48-linked diubiquitin (K48-diUb) fluctuates among three distinct conformational states, and a preexisting compact state is selectively enriched by Rpn13NTD. The same binding mode is observed for full-length Rpn13 and longer K48-linked Ub chain. Using solution NMR spectroscopy, we have solved the complex structure between Rpn13NTD and K48-diUb. In the structure, Rpn13NTD simultaneously interacts with proximal and distal Ub subunits of K48-diUb that remain associated in the complex, thus corroborating smFRET findings. The proximal Ub interacts with Rpn13NTD similarly as the Ub monomer in the known Rpn13NTD:Ub structure, while the distal Ub binds to a largely electrostatic surface of Rpn13NTD. Thus, a charge reversal mutation in Rpn13NTD can weaken the interaction between Rpn13 and K48-linked Ub chain, causing accumulation of ubiquitinated proteins. Moreover, blockage of the access of the distal Ub to Rpn13NTD with a proximity attached Ub monomer can also disrupt the interaction between Rpn13 and K48-diUb. Together, the bivalent interaction of K48-linked Ub chain with Rpn13 provides the structural basis for Rpn13 linkage selectivity, which opens a new window for modulating proteasomal function.


2021 ◽  
Author(s):  
Gabriela Garcia-Rodriguez ◽  
Daniel Charlier ◽  
Dorien Wilmaerts ◽  
Jan Michiels ◽  
Remy Loris

ABSTRACTThe rnlAB toxin-antitoxin operon from Escherichia coli functions as an anti-phage defense system. RnlA was recently identified as a member of the HEPN (Higher Eukaryotes and Prokaryotes Nucleotide-binding domain) superfamily of ribonucleases. The activity of the toxin RnlA requires tight regulation by the antitoxin RnlB, the mechanism of which remains unknown. Here we show that RnlA exists in an equilibrium between two different homodimer states: an inactive resting state and an active canonical HEPN dimer. Mutants interfering with the transition between states show that canonical HEPN dimerization via the highly conserved RX4-6H motif is required for activity. The antitoxin RnlB binds the canonical HEPN dimer conformation, inhibiting RnlA by blocking access to its active site. Single-alanine substitutions mutants of the highly conserved R255, E258, R318 and H323 show that these residues are involved in catalysis and substrate binding and locate the catalytic site near the dimer interface of the canonical HEPN dimer rather than in a groove located between the HEPN domain and the preceding TBP-like domain. Overall, these findings elucidate the structural basis of the activity and inhibition of RnlA and highlight the crucial role of conformational heterogeneity in protein function.


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