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Are tyrosine residues involved in the photoconversion of the water‐soluble chlorophyll‐binding protein of Chenopodium album ?
Author(s) -
Takahashi S.,
Seki Y.,
Uchida A.,
Nakayama K.,
Satoh H.
Publication year - 2015
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1111/plb.12274
Subject(s) - tyrosine , mutant , chemistry , stereochemistry , biology , biochemistry , gene
Non‐photosynthetic and hydrophilic chlorophyll ( C hl) proteins, called water‐soluble C hl‐binding proteins ( WSCP s), are distributed in various species of C henopodiaceae, A maranthaceae, P olygonaceae and B rassicaceae. Based on their photoconvertibility, WSCP s are categorised into two classes: Class I (photoconvertible) and Class II (non‐photoconvertible). C henopodium album WSCP ( C a WSCP ; Class I) is able to convert the chlorin skeleton of C hl a into a bacteriochlorin‐like skeleton under light in the presence of molecular oxygen. Potassium iodide ( KI ) is a strong inhibitor of the photoconversion. Because KI attacks tyrosine residues in proteins, tyrosine residues in C a WSCP are considered to be important amino acid residues for the photoconversion. Recently, we identified the gene encoding C a WSCP and found that the mature region of C a WSCP contained four tyrosine residues: T yr13, T yr14, T yr87 and T yr134. To gain insight into the effect of the tyrosine residues on the photoconversion, we constructed 15 mutant proteins (Y13A, Y14A, Y87A, Y134A, Y13‐14A, Y13‐87A, Y13‐134A, Y14‐87A, Y14‐134A, Y87‐134A, Y13‐14‐87A, Y13‐14‐134A, Y13‐87‐134A, Y14‐87‐134A and Y13‐14‐87‐134A) using site‐directed mutagenesis. Amazingly, all the mutant proteins retained not only chlorophyll‐binding activity, but also photoconvertibility. Furthermore, we found that KI strongly inhibited the photoconversion of Y13‐14‐87‐134A. These findings indicated that the four tyrosine residues are not essential for the photoconversion.