The conserved His-144 in the PsbP protein is important for the interaction between the PsbP N-terminus and the Cyt b559 subunit of photosystem II.
The PsbP protein regulates the binding properties of Ca(2+) and Cl(-), and stabilizes the Mn cluster of photosystem II (PSII); however, the binding site and topology in PSII have yet to be clarified. Here we report that the structure around His-144 and Asp-165 in PsbP, which is suggested to be a metal binding site, has a crucial role for the functional interaction between PsbP and PSII. The mutated PsbP-H144A protein exhibits reduced ability to retain Cl(-) anions in PSII, whereas the D165V mutation does not affect PsbP function. Interestingly, H144A/D165V double mutation suppresses the effect of H144A mutation, suggesting that these residues have a role other than metal binding. FTIR difference spectroscopy suggests that H144A/D165V restores proper interaction with PSII and induces the conformational change around the Mn cluster during the S(1)/S(2) transition. Cross-linking experiments show that the H144A mutation affects the direct interaction between PsbP and the Cyt b(559) α subunit of PSII (the PsbE protein). However, this interaction is restored in the H144A/D165V mutant. In the PsbP structure, His-144 and Asp-165 form a salt bridge. H144A mutation is likely to disrupt this bridge and liberate Asp-165, inhibiting the proper PsbP-PSII interaction. Finally, mass spectrometric analysis has identified the cross-linked sites of PsbP and PsbE as Ala-1 and Glu-57, respectively. Therefore His-144, in the C-terminal domain of PsbP, plays a crucial role in maintaining proper N terminus interaction. These data provide important information about the binding characteristics of PsbP in green plant PSII.
Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
Kunio
K
Ido
Shusuke
S
Kakiuchi
Chihiro
C
Uno
Taishi
T
Nishimura
Yoichiro
Y
Fukao
Takumi
T
Noguchi
Fumihiko
F
Sato
Kentaro
K
Ifuku
D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D002118:Calcium / Q000737:chemistry; D002234:Carbodiimides / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D003198:Computer Simulation; D017124:Conserved Sequence; D003432:Cross-Linking Reagents / Q000737:chemistry; D006639:Histidine / Q000737:chemistry* / Q000235:genetics; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010100:Oxygen / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics; D017550:Spectroscopy, Fourier Transform Infrared; D018724:Spinacia oleracea
C518491:1-ethyl-3-(3-(diethylamino)propyl)carbodiimide; D002234:Carbodiimides; D002712:Chlorides; D003432:Cross-Linking Reagents; D010446:Peptide Fragments; D045332:Photosystem II Protein Complex; D021122:Protein Subunits; D006639:Histidine; D010100:Oxygen; D002118:Calcium