PsaE is a 69 amino acid polypeptide from photosystem I present on the stromal side of the thylakoid membrane [1]. The structure is comprised of a well-defined five-stranded beta-sheet similar to SH3 domains [1].

1: Three-dimensional solution structure of PsaE from the cyanobacterium Synechococcus sp. strain PCC 7002, a photosystem I protein that shows structural homology with SH3 domains. Falzone CJ, Kao YH, Zhao J, Bryant DA, Lecomte JT; Biochemistry 1994;33:6052-6062. PMID:8193119