>TIGR01812 sdhA_frdA_Gneg succinate dehydrogenase or fumarate reductase, flavoprotein subunit; InterPro: IPR014006 Succinate:quinone oxidoreductase (1.3.5.1 from EC) refers collectively to succinate:quinone reductase (SQR, or Complex II) and quinol:fumarate reductase (QFR) . SQR is found in aerobic organisms, and catalyses the oxidation of succinate to fumarate in the citric acid cycle and donates the electrons to quinone in the membrane. QFR can be found in anaerobic cells respiring with fumarate as terminal electron acceptor. SQR and QFR are very similar in composition and structure, despite catalysing opposite reactions in vivo. They are thought to have evolved from a common ancestor, and in Escherichia coli they are capable of functionally replacing each other . Succinate:quinone oxidoreductases consist of a peripheral domain, exposed to the cytoplasm in bacteria and to the matrix in mitochondria, and a membrane-integral anchor domain that spans the membrane (Fig. 1). The peripheral part, which contains the dicarboxylate binding site, is composed of a flavoprotein subunit, with one covalently bound FAD, and an iron-sulphur protein subunit containing three iron-sulphur clusters. The membrane-integral domain functions to anchor the peripheral domain to the membrane and is required for quinone reduction and oxidation. The anchor domain shows the largest variability in composition and primary sequence, being composed either of one large subunit, or two smaller subunits, which may, or may not, contain protoheme groups. This entry represents the flavoprotein subunit found in both the SQR and QFR enzymes. This subunit contains an N-terminal domain which binds the FAD cofactor, a central catalytic domain with an unsual fold, and a C-terminal domain whose role is unclear , , . The dicarboxylate binding site is located between the FAD and catalytic domains..

Probab=97.99 E-value=3.1e-05 Score=54.38 Aligned_cols=178 Identities=19% Similarity=0.214 Sum_probs=96.6 Q ss_pred CEECCHHHHHHHHHHHHHCC---CEEEEEECCCCCCCC-------------------------------CCEE------- Q ss_conf 38775389999999999779---859999568765557-------------------------------7136------- Q gi|254780168|r 1 MIIGAGISGLTLAASLGHRG---IQSCVLEKKDQLSDS-------------------------------GFGI------- 39 (380) Q Consensus 1 iIvGaG~aGl~~A~~L~~~G---~~v~i~Er~~~~~~~-------------------------------g~gi------- 39 (380) T Consensus 3 vIVGaGgAGlRAA~e~a~~gPp~~~~AvisKvyP~RSHtvAAQGG~~Aal~~n~d~~D~~e~H~yDTVKGsDyLaDQDAv 82 (636) T TIGR01812 3 VIVGAGGAGLRAAVEAAKAGPPNLNVAVISKVYPTRSHTVAAQGGIAAALANNVDPDDSWEWHAYDTVKGSDYLADQDAV 82 (636) T ss_pred EEECCCHHHHHHHHHHHHCCCCCCEEEEEECCCCCCCCCHHHHHHHHHHHCCCCCCCCCCCCCEEEEECCCCCCHHHHHH T ss_conf 88818668999999997357796107999556988520153567899995778643207212304110144213258999 Q ss_pred ----EECHHHHHHHHHCCC-HHHHH---------HCCCCCCCEEEEECCCCCCCCCCCCCCCCCCCCCC----EEEEEEC Q ss_conf ----678889999998899-47898---------62688430699978854433345543234444782----4786200 Q gi|254780168|r 40 ----QISPNASRILKRIGI-LDQLE---------DIWIEPEDFVFRSGSTLKELSRFSCKNYSRNNWGG----IYGVVKR 101 (380) Q Consensus 40 ----~l~p~~~~~L~~lGi-~~~~~---------~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~----~~~~i~r 101 (380) T Consensus 83 e~~~~~AP~~v~eLe~wG~PfSR~~kGDRmaiinaqkttiteeDfRDG~IaQ----R~FGG~~~~~Gg~~a~RTcyAADk 158 (636) T TIGR01812 83 EYMCKEAPKAVLELERWGVPFSRLPKGDRMAIINAQKTTITEEDFRDGRIAQ----RPFGGASFDYGGAAARRTCYAADK 158 (636) T ss_pred HHHHHHCCHHHHHHHHCCCCCCCCCCCCEEEEEECCCCEECCCCCCCCCEEE----CCCCCCCCCCCCCHHHHHHHHHCC T ss_conf 9998515178999973789856786776477762454200201155883534----378888865566222134200121 Q ss_pred --CHHHHHHHHHHHHCCCEEEEEEEC-------------CCCCCCCCCCCCCC--EEEEEEEEECCCCCCCHHHCCCCCC Q ss_conf --013478899732068725642101-------------23443211234531--0356899743676631211285334 Q gi|254780168|r 102 --HTLQKILLNHIQTQPLARLHLSTH-------------ITHPDCTQISKINN--QKPDLLVGADGLNSNIRHYIDTQPI 164 (380) Q Consensus 102 --~~l~~~L~~~~~~~~~~~~~~~~~-------------v~~~~~~~~~~~~~--~~adlvIgADG~~S~vR~~l~~~~~ 164 (380) T Consensus 159 TGh~~LHTLye~~l~~~~V~ff~E~fa~~L~~~~~~GP~~~Gvva~~l~~G~~~~~~AKaVv~ATGG~GR~Y~~~tTNa~ 238 (636) T TIGR01812 159 TGHALLHTLYEQCLKLDGVEFFNEYFALDLILDQDGGPRVRGVVAYDLKTGEIVFFRAKAVVLATGGYGRVYKFTTTNAH 238 (636) T ss_pred CCHHHHHHHHHHHHCCCCCEEEHHHHHHHHHHHCCCCCEEEEEEEEEECCCEEEEEEECCEEEEECCCHHHHCCCCCCCE T ss_conf 13147898999985379942753888877887458986799999998058808999607489830651021030445442 Q ss_pred CCCCC---EEEEEECC-CCCCC Q ss_conf 43110---15786036-54465 Q gi|254780168|r 165 TFSGD---VVLRCLIP-QNNAP 182 (380) Q Consensus 165 ~~~~~---~~~~~~i~-~~~~~ 182 (380) T Consensus 239 ~~TGDG~A~AlraG~PqL~DME 260 (636) T TIGR01812 239 INTGDGLAMALRAGVPQLKDME 260 (636) T ss_pred EECCCHHHHHHHHCCCCCCCCC T ss_conf 2354068888873464316844

HHsearch alignment for GI: 254780168 and conserved domain: TIGR01812