1ZP0,2FBW,1YQ4


Conserved Protein Domain Family
SQR_TypeC_CybS

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cd03496: SQR_TypeC_CybS 
Click on image for an interactive view with Cn3D
SQR catalyzes the oxidation of succinate to fumarate coupled to the reduction of quinone to quinol. Eukaryotic SQRs reduce high potential quinones such as 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. CybS and CybL are the two transmembrane proteins of eukaryotic SQRs. They contain heme and quinone binding sites. CybS is the eukaryotic homolog of the bacterial SdhD subunit. The two-electron oxidation of succinate in the flavoprotein active site is coupled to the two-electron reduction of quinone in the transmembrane 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. Mutations in human Complex II result in various physiological disorders including hereditary paraganglioma and pheochromocytoma tumors. The gene encoding for the SdhD subunit is classified as a tumor suppressor gene.
Statistics
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PSSM-Id: 239576
Aligned: 31 rows
Threshold Bit Score: 107.709
Created: 10-Feb-2006
Updated: 2-Oct-2020
Structure
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Program:
Drawing:
Aligned Rows:
 
Conserved site includes 2 residues -Click on image for an interactive view with Cn3D
Feature 1:proximal heme binding site [chemical binding site]
Evidence:
  • Structure:1ZP0; Sus scrofa mitochondrial Respiratory Complex II membrane anchor subunits bind heme; contacts at 3.5A
  • Structure:2FBW; Gallus gallus Respiratory Complex II membrane anchor subunits bind heme; contacts at 3.5A
  • 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 membrane anchor subunits.

Sequence Alignment
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Format: Row Display: Color Bits: Type Selection:
Feature 1                                                  #   #                                 
1ZP0_D         4 KAASLHWTGERVVSVLLLGLLPAAYLNpCSAMDYSLAAALTLHGHWGIGQVVTDYVR----GDALQKAAKAGLLALSAFT 79  pig
NP_001004004  59 KAATMHWTGERILSIALLSLAPVAYFCpSPAVDYSLAAALTLHGHWGLGQVVTDYVH----GDAKIKMANAGLFVLSTVT 134 zebrafish
XP_792876     49 LLPSKHWNAERVLSIGLIGIIPAAFLIqNPALDYALAASLVLHGHWGMEQVFLDYVH----GETMSKVANASLFAISALS 124 purple urchin
AAQ18144      54 ALASTHWNAERVLVLSMLGLFPLAYFVqNPAVDYGLAAAVVLHGHWGFEQILTDYIH----GPLLPRLSKLALYGGSVLA 129 Branchiostoma b...
EAA06691      20 GSHVTLWNAERALSVALLGVIPVGLMFpSQVGDTLIAVSVVMHQHWGLEAIVTDYVRpilfGTTVPKLAHGLLLLVSAAT 99  Anopheles gambi...
AAL49239      71 SSHTLLWTVERIVSAGLLAVIPAAFIApSQVLDALMAISVVIHTHWGVEAMVVDYMRpsvvGNVLPKVAHIALIIISVAT 150 fruit fly
AAY66920      61 ANYVNIWKAERLLAASLLAVIPGAFMFpNAVMDSLLAISVTMHLHWGVETIVVDYVRpsifGAMIPKVAVGAVYALSISA 140 black-legged tick
BAA11233      53 HSHGTLFKIERYFAAAMVPLIPAAYFIhGREMDLCLALALTLHVHWGVWGVVNDYGRpfvlGDTLAAAVRVGAYIFTACL 132 pig roundworm
BAB84192      38 EDHSLHFKIERYWAAGMIPLIPTAYFIhTPAMDAVLTVAIVLHVHWGIAGVVSDYARpfviGDTLARVARASVYIITVIL 117 pig roundworm
CAB04259      42 PDHSMHFKLERLWAVGMLPILPASYFIhGPVMDAVLTVALTLHIHWGIHGVVYDYARpyviGEAAAKAAHVGVYLITGLL 121 nematode
Feature 1                               
1ZP0_D        80 FAGLCYFNYHDVGICKAVAMLWK 102 pig
NP_001004004 135 FAGLCYFNYHDVGICKAVALLWS 157 zebrafish
XP_792876    125 FAGLCYFNYNDVGLTKAVMMLWS 147 purple urchin
AAQ18144     130 FAGLCYFNYNDVGITKAISMIWH 152 Branchiostoma belcheri tsingtaunese
EAA06691     100 LGGLFYFNYNDIGIAGFVRKIWS 122 Anopheles gambiae str. PEST
AAL49239     151 LGGLFYFIQNDVGLANGIKRFWA 173 fruit fly
AAY66920     141 LVGLLYFNFTDVGIVKAVQLVWS 163 black-legged tick
BAA11233     133 LAGLLYFNEHDVGLTRAFEMVWE 155 pig roundworm
BAB84192     118 LASLLHFNNSDVGLTKAFEMVWS 140 pig roundworm
CAB04259     122 LGALLHFNTNDVGITKAFELVFS 144 nematode

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