InterPro domain: IPR036579

PsaD is a small, extrinsic polypeptide located on the stromal side (cytoplasmic side in cyanobacteria) of the photosystem I reaction centre complex. It is required for native assembly of PSI reaction clusters and is implicated in the electrostatic binding of ferredoxin within the reaction centre [ 1 ]. PsaD forms a dimer in solution which is bound by PsaE however PsaD is monomeric in its native complexed PSI environment [ 2 ].

Structurally, PsaD has a beta-BETA(2)-beta-alpha-beta(2) fold with antiparallel sheet packed against helix, has BETA-hairpin on the same side and has an irregular C-terminal tail.

1. Structure and properties in solution of PsaD, an extrinsic polypeptide of photosystem I. Eur. J. Biochem. 255, 309-16