Question

• A picture of the crystal structure of Human P-type ATpase protein and a description of its 2°, 3° and 4° structure

Answer 1

The crystal structure of P Type ATpase protein is

Basic structure of P-type ATPases –

Primary structure

It has five functional and structurally distinct domains – a) three cytoplasmic domains (A, actuator; N, nucleotide binding; P, phosphorylation) and b) and two membrane-embedded domains (T, transport; S, class specific support domain). It also comprises of a fourth domain i.e the regulatory (R) domain located at the N or C terminus or both.

Second Degree structure of P-type ATPase –

The membrane embedded domain T and S are imbedded in the cytoplasmic domains (A, P, and N). The N domain comprises of built-in P -domain phosphorylated protein kinase. Ca 2+ bind in the middle of the T-domain and is exposed to the cytoplasm and the extra cytoplasmic side.

Third degree Structure of P-type ATPase–

P-domain then phosphorylates at Asp residue by the N-domain. It is then dephosphorylated by the A-domain in a manner that the A-domain acts as a protein phosphatase while P domain serves as substrate for both the protein kinase and phosphatase

Tertiary Structure of P-type ATPase–

As the N-domain inserts into the P-domain, they together form second and larger cytoplasmic loop. Also the A domain is formed of the first cytoplasmic loop developed by it N-terminal extension