Site-directed mutagenesis of conserved C-terminal tyrosine and tryptophan residues of PsbO, the photosystem II manganese-stabilizing protein, alters its activity and fluorescence properties.
Biochemistry
; 47(24): 6490-8, 2008 Jun 17.
Article
em En
| MEDLINE
| ID: mdl-18500826
ABSTRACT
The extrinsic photosystem II PsbO subunit (manganese-stabilizing protein) contains near-UV CD signals from its complement of aromatic amino acid residues (one Trp, eight Tyr, and 13 Phe residues). Acidification, N-bromosuccinimide modification of Trp, reduction or elimination of a disulfide bond, or deletion of C-terminal amino acids abolishes these signals. Site-directed mutations that substitute Phe for Trp241 and Tyr242, near the C-terminus of PsbO, were used to examine the contribution of these residues to the activity and spectral properties of the protein. Although this substitution is, in theory, conservative, neither mutant binds efficiently to PSII, even though these proteins appear to retain wild-type solution structures. Removal of six residues from the N-terminus of the W241F mutant restores activity to near-wild-type levels. The near-UV CD spectra of the mutants are modified; well-defined Tyr and Trp peaks are lost. Characterizations of the fluorescence spectra of the full-length WF and YF mutants indicate that Y242 contributes significantly to PsbO's Tyr fluorescence emission and that an excited-state tyrosinate could be present in PsbO. Deletion of W241 shows that this residue is a major contributor to PsbO's fluorescence emission. Loss of function is consistent with the proposal that a native C-terminal domain is required for PsbO binding and activity, and restoration of activity by deletion of N-terminal amino acids may provide some insights into the evolution of this important photosynthetic protein.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fragmentos de Peptídeos
/
Proteínas de Plantas
/
Espectrometria de Fluorescência
/
Mutagênese Sítio-Dirigida
/
Complexo de Proteína do Fotossistema II
/
Manganês
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Estados Unidos
País de publicação:
EEUU
/
ESTADOS UNIDOS
/
ESTADOS UNIDOS DA AMERICA
/
EUA
/
UNITED STATES
/
UNITED STATES OF AMERICA
/
US
/
USA