mxaB

Gene Description

Response regulator (MxaB; historically moxB) that functions as a DNA-binding transcriptional regulator required for activation of the mxa operon encoding the Ca2+-dependent methanol dehydrogenase (MxaFI) system. It is located within the primary methanol oxidation (mxa/MOX) gene cluster. The protein has a LuxR-like / orphan response-regulator architecture - an N-terminal response regulatory (receiver) domain (residues 17-134) with a conserved aspartate phosphorylation site (D67) and a C-terminal HTH luxR-type DNA-binding/effector domain (residues 156-221). MxaB is part of the regulatory network coordinating the lanthanide-dependent metal switch between the Ca2+-dependent (MxaFI) and lanthanide-dependent (XoxF) methanol dehydrogenases; homolog data suggest it may act with the membrane histidine kinase MxaY as a non-traditional two-component system. There is no evidence that MxaB is an enzyme or transporter.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0000160 phosphorelay signal transduction system	IEA GO_REF:0000002	ACCEPT	Summary: MxaB is a response regulator (receiver domain residues 17-134, conserved aspartate D67) component of the methanol-oxidation regulatory network. Falcon deep research supports a LuxR-like / orphan response-regulator architecture that may pair with the membrane histidine kinase MxaY in a non-traditional two-component system controlling the lanthanide switch. Domain-based, but consistent with the literature. Supporting Evidence: file:METEA/mxaB/mxaB-deep-research-falcon.md the AM1 orphan response regulator MxaB is described as a LuxR-like transcription factor file:METEA/mxaB/mxaB-deep-research-falcon.md an associated membrane histidine kinase MxaY potentially forming a non-canonical two-component pair
GO:0003677 DNA binding	IEA GO_REF:0000120	ACCEPT	Summary: MxaB contains a C-terminal HTH luxR-type DNA-binding domain (residues 156-221). Falcon deep research confirms MxaB is treated as a DNA-binding transcriptional regulator (a LuxR-like transcription factor) of the mxa cluster, not an enzyme or transporter, supporting the DNA binding molecular function. Supporting Evidence: file:METEA/mxaB/mxaB-deep-research-falcon.md MxaB is a “LuxR-like transcription factor” file:METEA/mxaB/mxaB-deep-research-falcon.md No evidence retrieved indicates that MxaB is an enzyme or transporter.
GO:0006355 regulation of DNA-templated transcription	IEA GO_REF:0000002	ACCEPT	Summary: MxaB is required for activation of the mxa operon (canonical mxaFJGIRSACKLDEHB) encoding the Ca2+-dependent methanol dehydrogenase system, acting as a positive transcriptional regulator. Falcon deep research provides direct AM1 evidence (Roszczenko-Jasinska et al.) and genome-annotation context (Chistoserdova et al., who list moxB/mxaB as a transcriptional regulator in cluster 1 / MOX), strengthening this annotation beyond the IEA domain inference. Supporting Evidence: file:METEA/mxaB/mxaB-deep-research-falcon.md required for activation of the mxa operon (MxaB) file:METEA/mxaB/mxaB-deep-research-falcon.md This places MxaB as a positive regulator of expression of the canonical Ca\(2+\)-dependent methanol dehydrogenase system

Core Functions

MxaB functions as a DNA-binding transcriptional regulator required for activation of the mxa operon (canonical mxaFJGIRSACKLDEHB) encoding the Ca2+-dependent methanol dehydrogenase (MxaFI) system and accessory proteins. It contains an N-terminal response regulatory (receiver) domain (residues 17-134) with a conserved aspartate phosphorylation site (D67) and a C-terminal HTH luxR-type DNA-binding/effector domain (residues 156-221). MxaB is part of the regulatory network coordinating the lanthanide-dependent metal switch between the Ca2+-dependent (MxaFI) and lanthanide-dependent (XoxF) methanol oxidation systems; during the lanthanide switch the mxa operon is downregulated. As a LuxR-like / orphan response regulator it likely receives phosphorylation signals from the regulatory cascade, with homolog data suggesting it may form a non-traditional two-component system with the membrane histidine kinase MxaY. MxaB acts as a cytosolic/nucleoid-associated DNA-binding transcription factor and is not an enzyme or transporter.

Molecular Function:

DNA binding

Directly Involved In:

phosphorelay signal transduction system regulation of DNA-templated transcription

Supporting Evidence:

file:METEA/mxaB/mxaB-uniprot.txt
DOMAIN 17..134...Response regulatory...DOMAIN 156..221...HTH luxR-type...4-aspartylphosphate...DNA binding...phosphorelay signal transduction system...regulation of DNA-templated transcription
file:METEA/mxaB/mxaB-deep-research-falcon.md
required for activation of the mxa operon (MxaB)
file:METEA/mxaB/mxaB-deep-research-falcon.md
Cytosol/nucleoid-associated:** DNA-binding transcription factor that regulates transcription of the mxa operon

Gene Description

Existing Annotations Review

Core Functions

References

Deep Research

Falcon

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