Structural relationships between the SLC12 cotransporter C-terminal domain, universal stress proteins and adenylating enzymes

In phosphorylated NKCC1, D891 and D927 sit near the ATP phosphate chain and R801/K889 form a basic phosphate-binding clamp, defining the CTD nucleotide-site geometry.

• Why it matters: The ATP-binding CTD of SLC12 cotransporters is linked to universal stress proteins and adenylating enzymes, but how these folds relate structurally—and whether protein adenylation is feasible—was unclear.
• What they did: The authors analyzed 16,192 CTD-containing SLC12 sequences and compared 42,845 representative structures, then aligned NKCC1 CTD lobes against universal stress protein and EC-annotated adenylating-enzyme reference structures.
• The result: Both CTD lobes align structurally with universal stress proteins, form separate lineages including bacterial transporters, and suggest ATP positioning compatible with -phosphate chemistry, while candidate USP hydroxyls lack in-line attack geometry—supporting conditional protein adenylation tests requiring a covalent protein-AMP adduct and pyrophosphate coproduct detection.

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