ACT domains are commonly involved in specifically binding an amino acid or other small ligand leading to regulation of the enzyme; Members of this CD belong to the superfamily of ACT regulatory domains. Pairs of ACT domains are commonly involved in specifically binding an amino acid or other small ligand leading to regulation of the enzyme. The ACT domain has been detected in a number of diverse proteins; some of these proteins are involved in amino acid and purine biosynthesis, phenylalanine hydroxylation, regulation of bacterial metabolism and transcription, and many remain to be characterized. ACT domain-containing enzymes involved in amino acid and purine synthesis are in many cases allosteric enzymes with complex regulation enforced by the binding of ligands. The ACT domain is commonly involved in the binding of a small regulatory molecule, such as the amino acids L-Ser and L-Phe in the case of D-3-phosphoglycerate dehydrogenase and the bifunctional chorismate mutase-prephenate dehydratase enzyme (P-protein), respectively. Aspartokinases typically consist of two C-terminal ACT domains in a tandem repeat, but the second ACT domain is inserted within the first, resulting in, what is normally the terminal beta strand of ACT2, formed from a region N-terminal of ACT1. ACT domain repeats have been shown to have nonequivalent ligand-binding sites with complex regulatory patterns such as those seen in the bifunctional enzyme, aspartokinase-homoserine dehydrogenase (ThrA). In other enzymes, such as phenylalanine hydroxylases, the ACT domain appears to function as a flexible small module providing allosteric regulation via transmission of conformational changes, these conformational changes are not necessarily initiated by regulatory ligand binding at the ACT domain itself. ACT domains are present either singularly, N- or C-terminal, or in pairs present C-terminal or between two catalytic domains. Unique to cyanobacteria are four ACT domains C-terminal to an aspartokinase domain. A few proteins are composed almost entirely of ACT domain repeats as seen in the four ACT domain protein, the ACR protein, found in higher plants; and the two ACT domain protein, the glycine cleavage system transcriptional repressor (GcvR) protein, found in some bacteria. Also seen are single ACT domain proteins similar to the Streptococcus pneumoniae ACT domain protein (uncharacterized pdb structure 1ZPV) found in both bacteria and archaea. Purportedly, the ACT domain is an evolutionarily mobile ligand binding regulatory module that has been fused to different enzymes at various times.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1527573924 157 SLCCEDRSDLIPDLNEILKSFHLSPLKAEIVTLGGRVRNVIILAGDKSQ-TDDESVPSLRDALR 219
Cdd:cd04899     4 ELTALDRPGLLADVTRVLAELGLNIHSAKIATLGERAEDVFYVTDADGQpLDPERQEALRAALG 67

C-terminal ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD and related domains; This ACT domain family, ACT_ACR-UUR-like_2, includes the second of two C-terminal ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD; including those enzymes similar to the GlnD found in enteric Escherichia coli and those found in photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum. Also included in this CD are the second and fourth ACT domains of a novel protein composed almost entirely of ACT domain repeats, the ACR protein. These ACR proteins, found in Arabidopsis and Oryza, are proposed to function as novel regulatory or sensor proteins in plants. Members of this CD belong to the superfamily of ACT regulatory domains.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1527573924 157 SLCCEDRSDLIPDLNEILKSFHLSPLKAEIVTLGGRVRNVIILAGDKSQ-TDDESVPSLRDALR 219
Cdd:cd04899     4 ELTALDRPGLLADVTRVLAELGLNIHSAKIATLGERAEDVFYVTDADGQpLDPERQEALRAALG 67

Helix-loop-helix DNA-binding domain;

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                  ....*....|....*....|....*....|....*....|.
gi 1527573924  83 RERINSHLDKLRTLLPC---NTKTDKASLLAKVVQRVRELK 120
Cdd:pfam00010  13 RDRINDAFDELRELLPTlppDKKLSKAEILRLAIEYIKHLQ 53

C-terminal ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD and related domains; This ACT domain family, ACT_ACR-UUR-like_2, includes the second of two C-terminal ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD; including those enzymes similar to the GlnD found in enteric Escherichia coli and those found in photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum. Also included in this CD are the second and fourth ACT domains of a novel protein composed almost entirely of ACT domain repeats, the ACR protein. These ACR proteins, found in Arabidopsis and Oryza, are proposed to function as novel regulatory or sensor proteins in plants. Members of this CD belong to the superfamily of ACT regulatory domains.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1527573924 157 SLCCEDRSDLIPDLNEILKSFHLSPLKAEIVTLGGRVRNVIILAGDKSQ-TDDESVPSLRDALR 219
Cdd:cd04899     4 ELTALDRPGLLADVTRVLAELGLNIHSAKIATLGERAEDVFYVTDADGQpLDPERQEALRAALG 67

helix loop helix domain;

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                   ....*....|....*....|....*....|....*....|....*.
gi 1527573924   83 RERINSHLDKLRTLLPC---NTKTDKASLLAKVVQRVRELKQQTSE 125
Cdd:smart00353   8 RRKINEAFDELRSLLPTlpkNKKLSKAEILRLAIEYIKSLQEELQK 53

basic helix-loop-helix (bHLH) domain found in Arabidopsis thaliana phytochrome interacting factors (PIFs) and similar proteins; The family includes several bHLH transcription factors from Arabidopsis thaliana, such as PIFs, ALC, PIL1, SPATULA, and UNE10. PIFs (PIF1, PIF3, PIF4, PIF5, PIF6 and PIF7) have been shown to control light-regulated gene expression. They directly bind to the photoactivated phytochromes and are degraded in response to light signals. ALC, also termed AtbHLH73, or protein ALCATRAZ, or EN 98, is required for the dehiscence of fruit, especially for the separation of the valve cells from the replum. It promotes the differentiation of a strip of labile non-lignified cells sandwiched between layers of lignified cells. PIL1, also termed AtbHLH124, or protein phytochrome interacting factor 3-like 1, or EN 110, is involved in responses to transient and long-term shade. It is required for the light-mediated inhibition of hypocotyl elongation and necessary for rapid light-induced expression of the photomorphogenesis- and circadian-related gene APRR9. PIL1 seems to play a role in multiple PHYB responses, such as flowering transition and petiole elongation. SPATULA, also termed AtbHLH24, or EN 99, plays a role in floral organogenesis. It promotes the growth of carpel margins and of pollen tract tissues derived from them. UNE10, also termed AtbHLH16, or protein UNFERTILIZED EMBRYO SAC 10, or EN 99, is required during the fertilization of ovules by pollen.

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                  ....*....|....*....|....*....|....*....|....*....|..
gi 1527573924  71 ASQQHKEAERRRRERINSHLDKLRTLLPCNTKTDKASLLAKVVQRVRELKQQ 122
Cdd:cd11445     2 AAEVHNLSERRRRDRINEKMKALQELIPNCNKTDKASMLDEAIEYLKSLQLQ 53

ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD; This ACT domain family, ACT_UUR_ACR-like, includes the two C-terminal ACT domains of the bacterial signal-transducing uridylyltransferase /uridylyl-removing (UUR) enzyme, GlnD; including those enzymes similar to the GlnD found in enteric Escherichia coli and those found in photosynthetic, nitrogen-fixing bacterium Rhodospirillum rubrum. Also included in this CD are the four ACT domains of a novel protein composed almost entirely of ACT domain repeats (the ACR protein) and like proteins. These ACR proteins, found in Arabidopsis and Oryza, are proposed to function as novel regulatory or sensor proteins in plants. This CD also includes the first of the two ACT domains that comprise the Glycine Cleavage System Transcriptional Repressor (GcvR) protein and related domains, as well as, the N-terminal ACT domain of a yet characterized Arabidopsis/Oryza predicted tyrosine kinase. Members of this CD belong to the superfamily of ACT regulatory domains.

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                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1527573924 157 SLCCEDRSDLIPDLNEILKSFHLSPLKAEIVTLGGRVRNV-IILAGDKSQTDDESVPSLRDALR 219
Cdd:cd04873     4 EVYAPDRPGLLADITRVLADLGLNIHDARISTTGERALDVfYVTDSDGRPLDPERIARLEEALE 67