Small CinA C-terminal/PncC-family protein of Pseudomonas putida KT2440. The 167-residue protein carries the CinA/PncC domain signatures IPR008136, PF02464, and TIGR00199. Its catalytic activity, substrate specificity, and physiological role have not been established; membership in a family that includes inactive domains does not by itself establish NMN deamidase activity for this paralog.
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Download this section (compressed HTML)Q: Does PP_3298 encode an active NMN deamidase, another CinA-family specificity, or a catalytically inactive paralog?
Experiment: Purify Q88HQ5 and Q88ME5 side by side, measure substrate-dependent product formation rather than binding alone, and combine single/double deletions with targeted pyridine-nucleotide metabolomics before assigning a GO molecular function to PP_3298.
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The molecular activity, substrate specificity, and physiological role of PP_3298/Q88HQ5 are unknown. CinA-C/PncC-family domain assignments do not establish that this paralog deamidates NMN.
OPEN BIOLOGYCURATION MF_DARK
What is known: Q88HQ5 is a 167-residue TIGR00199/IPR008136/PF02464 protein and is the second compact CinA-C/PncC-family candidate in KT2440, but unlike Q88ME5/PncC it lacks a submitted NMN-amidohydrolase name, EC assignment, GO activity, or target-specific experiment.
Significance: Resolving this paralog is necessary to distinguish redundant NMN salvage from a different CinA-family activity or a catalytically inactive domain.
What would resolve it: Compare purified Q88HQ5 and Q88ME5 against NMN and plausible alternative substrates, verify reaction products, and test single and double mutants with targeted NMN, NaMN, and NAD+ metabolomics.
Provenance (the field's own admissions):
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