2HMF


Conserved Protein Domain Family
ACT_AKi-HSDH-ThrA-like_1

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cd04921: ACT_AKi-HSDH-ThrA-like_1 
Click on image for an interactive view with Cn3D
ACT domains of the bifunctional enzyme aspartokinase (AK) - homoserine dehydrogenase (HSDH)
This CD includes the first of two ACT domains of the bifunctional enzyme aspartokinase (AK) - homoserine dehydrogenase (HSDH). The ACT domains are positioned between the N-terminal catalytic domain of AK and the C-terminal HSDH domain found in bacteria (Escherichia coli (EC) ThrA) and higher plants (Zea mays AK-HSDH). AK and HSDH are the first and third enzymes in the biosynthetic pathway of the aspartate family of amino acids. AK catalyzes the phosphorylation of Asp to P-aspartyl phosphate. HSDH catalyzes the NADPH-dependent conversion of Asp 3-semialdehyde to homoserine. HSDH is the first committed reaction in the branch of the pathway that leads to Thr and Met. In E. coli, ThrA is subject to allosteric regulation by the end product L-threonine and the native enzyme is reported to be tetrameric. As with bacteria, plant AK and HSDH are feedback inhibited by pathway end products. Maize AK-HSDH is a Thr-sensitive 180-kD enzyme. Arabidopsis AK-HSDH is an alanine-activated, threonine-sensitive enzyme whose ACT domains were shown to be involved in allosteric activation. Also included in this CD is the first of two ACT domains of a tetrameric, monofunctional, threonine-sensitive, AK found in Methanococcus jannaschii and other related archaeal species. Members of this CD belong to the superfamily of ACT regulatory domains.
Statistics
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PSSM-Id: 153193
View PSSM: cd04921
Aligned: 37 rows
Threshold Bit Score: 79.5631
Threshold Setting Gi: 11498307
Created: 17-Apr-2006
Updated: 2-Oct-2020
Structure
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Program:
Drawing:
Aligned Rows:
 
Conserved site include 1 residue -Click on image for an interactive view with Cn3D
Feature 1:putative threonine allosteric regulatory site
Evidence:
  • Comment:potentially involved in the binding of Thr.
  • Comment:Kinetic experiments on Arabidopsis AK-HSDH showed that each regulatory (ACT) domain of the monomers contained two nonequivalent threonine binding sites, constituted in part by this conserved Gln residue of the ACT domain, and a conserved Gln residue lying outside this domain.
  • Comment:The interaction of threonine with this conserved Gln residue of the ACT in Arabidopsis AK-HSDH led to inhibition of AK activity and facilitated the binding of a second threonine on a conserved Gln residue lying outside this domain. Interaction of this second threonine with the latter led to inhibition of HSDH activity.
  • Comment:substitution of a Phe residue for a Ser immediately C-terminal to this ACT domain Gln revealed this Ser as a possible key residue involved with the allosteric regulation of both AKI and HSDHI activities.
  • Citation:PMID 8432719

Sequence Alignment
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Format: Row Display: Color Bits: Type Selection:
Feature 1                                           #                                           
2HMF_A      317 VALINIFGAGMvGVSGTAARIFKALGEeEVNVILISQGSSETNISLVVSEEDVDKALKALKREFGDfgkksflnnnlird 396 Methanocaldococc...
NP_662905   315 VVLLSLSGSGMaGVPGTASRLFTCLARhSINIIFISQASSEQSISLAIAPGQASMAKKVLEEEFAReieer-----ridp 389 Chlorobium tepid...
AAY49442    330 LAVLNLEGTGLiGVPGTAERVFAALRTaQVSVVMISQGSSEHSICCVVKQHESERARNALLQAFAHeltvg-----qvqr 404 Xanthomonas camp...
YP_444829   322 VALLNLEGSGMiGVPGIARRLFDALEDeGVSVILISQGSSEHSICFAVPQAQAEVAREAAEHAFYAeldrg-----qlrt 396 Salinibacter rub...
ZP_01060709 311 VALLTLEGGGMvGIPGISKRLFETLSNqGINIILITQASSEHSICLGVMEEDAGKAKNAIDEEFEYeisln-----kidp 385 Flavobacterium s...
ZP_01106318 313 IALLSLEGPGMvGVPGISKRFFEVLSQsNISVVLITQASSEHSICVGVSANDVAEAEQSVNDAFAYeisgg-----kikp 387 Flavobacteriales...
ZP_01244304 314 ISLVTLEGPGMiGVAGSSRRLFEVLSQeKINVIFITQASSEHSICIGILNSDADKAEAAINRAFEIeisqn-----kidp 388 Flavobacterium j...
YP_630499   316 IALVNLGGAGLkGVPGTAARVFESMALaNISVVLITQGSSECSISFCVQQADAERAVQALEVAFEMeraag-----kvdt 390 Myxococcus xanth...
YP_862002   314 IKLLNIEGSGMvGIPGFSKRFFEILFQeNINVVLITQASSEHSICIAVKDDEAEKAKEALDEAFEVeigyk-----kikp 388 Gramella forseti...
ZP_01690317 314 IALLRVSGSGMvGVPGVSSRIFGALAQhQINIVLISQASSEHSICFAVAPEDAKEAKEVIEEAFSLeiqak-----kvnk 388 Microscilla mari...
Feature 1            
2HMF_A      397 VSVDK 401 Methanocaldococcus jannaschii
NP_662905   390 VSVRR 394 Chlorobium tepidum TLS
AAY49442    405 VQLTT 409 Xanthomonas campestris pv. campestris str. 8004
YP_444829   397 VELVP 401 Salinibacter ruber DSM 13855
ZP_01060709 386 LTIEI 390 Flavobacterium sp. MED217
ZP_01106318 388 VIVES 392 Flavobacteriales bacterium HTCC2170
ZP_01244304 389 CYVEK 393 Flavobacterium johnsoniae UW101
YP_630499   391 IEQQR 395 Myxococcus xanthus DK 1622
YP_862002   389 VEIED 393 Gramella forsetii KT0803
ZP_01690317 389 VSIEQ 393 Microscilla marina ATCC 23134

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