Conserved Protein Domain Family
SQR_TypeC_SdhD

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cd03494: SQR_TypeC_SdhD 
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Succinate:quinone oxidoreductase (SQR) Type C subfamily, Succinate dehydrogenase D (SdhD) subunit; SQR catalyzes the oxidation of succinate to fumarate coupled to the reduction of quinone to quinol. E. coli SQR, a member of this subfamily, reduces the high potential quinine, ubiquinone. SQR is also called succinate dehydrogenase or Complex II, and is part of the citric acid cycle and the aerobic respiratory chain. SQR is composed of a flavoprotein catalytic subunit, an iron-sulfur protein and one or two hydrophobic transmembrane subunits. Members of this subfamily are classified as Type C SQRs because they contain two transmembrane subunits and one heme group. SdhD and SdhC are the two transmembrane proteins of bacterial SQRs. They contain heme and quinone binding sites. The two-electron oxidation of succinate in the flavoprotein active site is coupled to the two-electron reduction of quinone in the membrane anchor subunits via electron transport through FAD and three iron-sulfur centers. The reversible reduction of quinone is an essential feature of respiration, allowing transfer of electrons between respiratory complexes.
Statistics
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PSSM-Id: 239574
View PSSM: cd03494
Aligned: 32 rows
Threshold Bit Score: 78.0316
Threshold Setting Gi: 56314070
Created: 13-Feb-2006
Updated: 17-Jan-2013
Structure
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Program:
Drawing:
Aligned Rows:
 
Conserved site includes 5 residues -Click on image for an interactive view with Cn3D
Feature 1:proximal heme binding site [chemical binding site]
Evidence:
  • Structure:1NEK; Escherichia coli Succinate dehydrogenase binds heme; contacts at 3.5A
    View structure with Cn3D
  • Structure:2ACZ; Escherichia coli Succinate dehydrogenase binds heme; contacts at 3.5A
    View structure with Cn3D
  • Comment:Members of this subfamily contain one heme group, proximal to the [3Fe-4S] cluster of the iron-sulfur subunit. Two histidines from different membrane anchor subunits coordinate with iron in heme.
  • Comment:Heme is essential for functional assembly and structural stability of the transmembrane subunits.

Sequence Alignment
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Format: Row Display: Color Bits: Type Selection:
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
Feature 1               #   #                                            #  #   #               
1NEK_D       15 DFILVRATAIVLTLYIIYMVGFFATSGe---LTYEVWIGFFASa-FTKVFTLLALFSILIHAWIGMWQVLTDYVKpLALR 90
gi 82701991  18 DWLAQRVTAAVMAIYILMLAGVLLVSPp---QDYASFKTLFDNq-WMRVASFLFLLSLFWHAWIGMRNILMDYVHpAGIR 93
gi 7226188   15 DWVMQRATAVIMLIYTVALLVVLFSLP----KEYSAWQAFFSQt-WVKVFTQVSFIAVFLHAWVGIRDLWMDYIKpFGVR 89
gi 71548701  18 DWLVQRVTAVIMAVYTGLLIVLVVVYQp---EGYEEFKSLFSIq-WVKIASLLCFAGLCWHAWVGVRNVLMDYVHpMFIR 93
gi 76884244   6 AWLVQRGTAVIMLVLLLFFLARLMQGSf---KTYEAWREWISDp-LVSIMVALFFGVLLLHSWVGLRDIILDYVRpVSLR 81
gi 56314070   9 AWMLQRVTAVVLLIFLAAAAAMLLAGLp---LTYERWYELATSp-HGAVLIVVLFAALALHGWIGIRDIVLDYIHpPAVR 84
gi 56603744  18 DFFVQRVTAVIIAVYFGYLILEALYLShigaLNYDSWRGLFTDgmFFRVATLMAYLAMFFHAWVGIWIICGDYIKfAWAS 97
gi 71848098  15 DWIAQRATAVIMAVYSVLIAAVLLVVRp---NTFEAWQGVFANg-VIKFLTFLFFVSLFYHAWIGVRDIWMDYVKpTGVR 90
gi 34496521  15 DWIMQRVTAVVMVLYTVALALFLLALP----AGYEGWKSLFSHt-WVQLFTQVTLLALFLHVWVGIRDVWMDYVKpVGIR 89
gi 56315306  15 DWIGQRATAVFMVIFTILFAIAALRLPe---MTHEAWSGLFRSg-VMRFFTFLFFLALFYHAWIGVRDIFMDYINpVGVR 90
                        90       100
                ....*....|....*....|...
Feature 1                              
1NEK_D       91 LMLQLVIVVALVVYVIYGFVVVW 113
gi 82701991  94 LILEILVILSLLSYAIWSVEILW 116
gi 7226188   90 LFLQVATIVWLVGCLVYSVKVIW 112
gi 71548701  94 LTLQVMCIVALLGYLIWFLDILW 116
gi 76884244  82 LFAHSLIVVVYSGIGFWVIRILL 104
gi 56314070  85 LPLLGLIALVLIAIVIRVALTMA 107
gi 56603744  98 ALVMLSFVLVYIFCFFWLFAVLF 120
gi 71848098  91 LTLHVVTIAALVGYTAWAAAILW 113
gi 34496521  90 LALHVFTIVWLVSCFIYSVKVVW 112
gi 56315306  91 LVLHVVTIFVLVGYAGWAAQILW 113

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