P1Btype

P1Btype, in the context of membrane transport proteins, refers to the P1B subclass of P-type ATPases. These enzymes use energy from ATP hydrolysis to transport metal cations across biological membranes, playing a central role in metal homeostasis and detoxification in bacteria, plants, and animals.

The typical P1B-type ATPase architecture includes a conserved cytoplasmic actuator (A), phosphorylation (P), and nucleotide-binding (N) domains that coordinate ATP hydrolysis, together with a transmembrane core that forms the metal translocation pathway. A characteristic phosphorylation site within the P-domain features the DKTGT motif. Many P1B-type pumps also possess N-terminal regulatory metal-binding domains rich in cysteine motifs (for example CXXC), which bind metal ions and influence activity. Some motifs within transmembrane segments, such as CPC, contribute directly to metal coordination in the transport site.

Substrates of P1B-type ATPases are diverse and include copper (Cu+), zinc (Zn2+), cobalt (Co2+), nickel (Ni2+), cadmium (Cd2+), and sometimes lead (Pb2+). In bacteria, P1B-type pumps commonly participate in copper resistance and zinc homeostasis. In eukaryotes, copper-transporting P1B-type ATPases (e.g., ATP7A and ATP7B in humans) deliver copper to secretory pathway enzymes and contribute to systemic copper distribution; mutations in these genes cause Menkes and Wilson diseases, illustrating the medical relevance of this family.

Genomic and functional studies show that P1B-type ATPases often operate alongside metallochaperones and regulatory proteins that sense metal availability and adjust expression or trafficking. Structural and biochemical work continues to elucidate the precise mechanisms of metal recognition, selectivity, and coupling to ATP hydrolysis.