Refined crystal structure of phycoerythrin from Porphyridium cruentum at 0.23‐nm resolution and localization of the γ subunit

Abstract

The three‐dimensional structure of the light‐harvesting pigment‐protein b‐phycoerythrin from the red alga Porphyridium cruentum has been determined at 0.23‐nm resolution. The b‐phycoerythrin structure is very similar to the structure of B‐phycoerythrin from Porphyridium sordidum. Besides three non‐identical residues there are only small differences between b‐phycoerythrin and B‐phycoerythrin α and β subunits, respectively. In the crystals b‐phycoerythrin forms an (αβ)6 hexamer (molecular mass: 236 kDa), whereas B‐phycoerythrin additionally contains a 30‐kDa γ subunit. The comparison of the b‐phycoerythrin and B‐phycoerythrin electron‐density maps clearly reveals, that the γ subunit is located inside the (αβ)6 aggregate. Copyright © 1993, Wiley Blackwell. All rights reserved