FUNCTIONAL CHARACTERIZATION OF THE EVOLUTIONARILY DIVERGENT FERN PLASTOCYANIN

摘要

Plastocyanin is a soluble copper protein that transfers electrons from cytochrome b_6f photosystem I (PSI) (Hope 2000). All eukaryotic plastocyanins possess an almost identical global fold, and its surface electrostatic potential distribution plays akey role in complex formation with the two membrane partners. In a typical plant plastocyanin, the 'east side', comprising negatively charged residues, has been proposed to be involved in electrostatic interactions with both PSI and cytochrome f, whereasthe hydrophobic patch, at the so-called 'northern side' of the protein, constitutes the electron transfer pathway (Sigfridsson 1998, Hope 2000). While maintaining the same global structure, fern plastocyanin has an acidic region that is relocated and surrounds the hydrophobic patch, resulting in very distinct electrostatic properties as compared to typical eukaryotic plastocyanins (Kohzuma et al 1999).