OpgI is a small 66-residue protein encoded between opgG and opgH in Cereibacter sphaeroides 2.4.1. Its locus is required for native osmoregulated periplasmic glucan production and can be complemented in trans with appropriately expressed opgI. The protein-specific molecular contribution is unresolved. An ACP-like accessory role has been proposed, while translational coupling remains an alternative explanation for its contribution to heterologous OpgH expression.
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Download this section (compressed HTML)Q: Does purified OpgI directly bind or activate OpgH, stabilize its assembly, or affect OpgH production through a different mechanism?
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: The molecular work performed by OpgI during native OPG synthesis is unknown; an ACP-like accessory activity has not been demonstrated.
What is known: Native2.4.1 insertion/complementation establishes an opgI requirement, and the corrected 66-residue ORF maps exactly to Q3J1N3. Heterologous opgIH restoration does not separate a protein cofactor from translational coupling.
Provenance (the field's own admissions):
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