aqpZ

UniProt ID: Q88F17
Organism: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950 / KT2440)
Review Status: DRAFT
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Gene Description

aqpZ encodes aquaporin Z, an inner-membrane water-selective channel that mediates rapid osmotically driven water movement. Falcon deep research confirms the MIP/aquaporin family assignment and orthology-based inference of a homotetrameric, water-selective (not glycerol-permeable) channel, while noting that no primary experimental study directly characterizes the P. putida KT2440 ortholog (PP_4282/Q88F17).

Existing Annotations Review

GO Term Evidence Action Reason
GO:0005886 plasma membrane
IEA
GO_REF:0000120 		ACCEPT
Summary: The bacterial plasma-membrane annotation is correct for AqpZ.
Reason: UniProt places AqpZ in the cell inner membrane, corresponding to plasma membrane in bacterial GO annotation, and membrane localization is intrinsic to its channel function.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
SUBCELLULAR LOCATION: Cell inner membrane
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0005886 plasma membrane
file:PSEPK/aqpZ/aqpZ-deep-research-falcon.md
PP_4282 is expected to localize to the **cytoplasmic (inner) membrane** of this Gram-negative bacterium and form tetramers, with **one functional water pore per monomer**.
GO:0006833 water transport
IEA
GO_REF:0000120 		ACCEPT
Summary: Water transport is the correct process annotation for AqpZ.
Reason: UniProt describes osmotically driven movement of water through AqpZ in both directions.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
Channel that permits osmotically driven movement of water
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0006833 water transport
file:PSEPK/aqpZ/aqpZ-deep-research-falcon.md
AqpZ in canonical bacterial contexts supports **rapid water influx/efflux during sudden osmotic shifts** (hypo-osmotic induction noted; role in osmoregulation and competitive viability).
GO:0015250 water channel activity
IEA
GO_REF:0000120 		ACCEPT
Summary: Water channel activity is the core molecular function of AqpZ.
Reason: The specific aquaporin channel annotation matches the UniProt function and Rhea water transport reaction.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
Reaction=H2O(in) = H2O(out)
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0015250 water channel activity
file:PSEPK/aqpZ/aqpZ-deep-research-falcon.md
functional data summarized in authoritative prokaryotic aquaporin reviews indicate that AqpZ behaves as an “exclusive water facilitator” (water transport detectable; glycerol/urea transport not detected in standard assays).
GO:0015267 channel activity
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: This channel parent term is true but less informative than water channel activity.
Reason: GO:0015250 captures the substrate-specific channel function and should be preferred over the broad channel-activity parent.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
Aquaporin Z
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0015267 channel activity
GO:0016020 membrane
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: The generic membrane annotation is true but redundant with plasma membrane.
Reason: GO:0005886 is a more informative location for this bacterial inner-membrane channel.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
Cell inner membrane
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0016020 membrane
GO:0055085 transmembrane transport
IEA
GO_REF:0000002 		MARK AS OVER ANNOTATED
Summary: This process parent is true but less informative than water transport.
Reason: GO:0006833 captures the substrate-specific transport process for AqpZ.
Supporting Evidence:
file:PSEPK/aqpZ/aqpZ-uniprot.txt
movement of water in
file:PSEPK/aqpZ/aqpZ-goa.tsv
GO:0055085 transmembrane transport

Core Functions

Inner-membrane aquaporin water channel that permits bidirectional osmotic water movement.

Molecular Function:
water channel activity
Directly Involved In:
water transport
Cellular Locations:
plasma membrane
Supporting Evidence:
  • file:PSEPK/aqpZ/aqpZ-uniprot.txt
    Channel that permits osmotically driven movement of water
  • file:PSEPK/aqpZ/aqpZ-uniprot.txt
    Reaction=H2O(in) = H2O(out)
  • file:PSEPK/aqpZ/aqpZ-deep-research-falcon.md
    Q88F17 is best annotated as a **water-selective aquaporin (AqpZ-like)** that increases membrane water permeability.
  • file:PSEPK/aqpZ/aqpZ-deep-research-falcon.md
    AqpZ (Q88F17) is likely an inner-membrane aquaporin that facilitates rapid, selective transmembrane water flux (osmotic water permeability).

References

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Suggested Questions for Experts

Q: Does KT2440 AqpZ measurably contribute to osmotic-shock survival under the environmental conditions where P. putida encounters rapid osmolarity changes?

Suggested Experiments

Experiment: Compare osmotic downshock survival and stopped-flow water permeability in wild-type, aqpZ knockout, and complemented strains.

Type: osmotic-shock and membrane permeability assay

Deep Research

Falcon

(aqpZ-deep-research-falcon.md)

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