Related Experiment Video
Updated: Aug 12, 2026

Protein-protein Interactions Visualized by Bimolecular Fluorescence Complementation in Tobacco Protoplasts and Leaves
Published on: March 9, 2014
The primary structure of a cDNA for PsaN, encoding an extrinsic lumenal polypeptide of barley photosystem I
1Department of Physiology, Carlsberg Laboratory, Copenhagen Valby, Denmark.
Abstract:
A cDNA clone encoding a 15,501 Da photosystem I (PSI) subunit of barley was isolated using an oligonucleotide based on the NH2-terminal amino acid sequence of the isolated protein. The polypeptide, which migrates with an apparent molecular mass of 9.5 kDa on denaturing SDS-PAGE, has been designated PSI-N, and the corresponding gene is PsaN. Analysis of the deduced protein sequence indicates a mature protein of 85 amino acid residues and a molecular mass of 9818 Da. PSI-N is a hydrophilic, extrinsic protein with no predicted membrane-spanning regions. The transit peptide of 60 residues (5683 Da) contains a predicted hydrophobic alpha-helix, suggesting that the protein is routed into the thylakoid lumen. Thus, PSI-N is the second known lumenal protein component associated with PSI, together with PSI-F.
Related Concept Videos
Photosystem II
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Photosystem I
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
The Central Dogma
The Antenna Complex
Photosystems
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Protein Transport to the Outer Chloroplast Membrane
Two models describe the mechanism of precursor recognition and entry across the outer membrane through the TOC complex. Model 1 suggests the newly synthesized precursor binds to the TOC receptor 159 and forms a complex.

