Crystal Structure of Chloroplastic Ascorbate Peroxidase from Tobacco Plants and Structural Insights into its Instability

Ascorbate peroxidase (APX) is a heme-containing protein that plays a central role in scavenging H2O2 in higher plants. The structure of stromal APX (sAPX) was determined at 1.6 Å to an R-factor of 19.1% and an R-free-factor of 22.3%. The electrostatic potential of the γ-channel that connects the mo...

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Bibliographic Details
Published in:Journal of biochemistry (Tokyo) 2003-08, Vol.134 (2), p.239-244
Main Authors: Wada, Kei, Tada, Toshiji, Nakamura, Yoshihiro, Ishikawa, Takahiro, Yabuta, Yukinori, Yoshimura, Kazuya, Shigeoka, Shigeru, Nishimura, Keiichiro
Format: Article
Language:English
Subjects:
APX
AsA
ascorbate
ascorbate peroxidase
Ascorbate Peroxidases
Binding Sites
cAPX
CCP
chloroplastic isoenzyme
Chloroplasts - enzymology
crystal structure
Crystallography, X-Ray
cytochrome c peroxidase
cytosolic ascorbate peroxidase
Enzyme Stability
hydrogen peroxide
instability
Isoenzymes
lignin peroxidase
LiP
manganese peroxidase
mAPX
microbody-bound ascorbate peroxidase
MnP
Models, Molecular
Nicotiana - enzymology
Peroxidases - chemistry
Pisum sativum - enzymology
Protein Structure, Secondary
sAPX
Static Electricity
stromal ascorbate peroxidase
tAPX
thylakoid-bound ascorbate peroxidase
Yeasts - enzymology
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Summary:Ascorbate peroxidase (APX) is a heme-containing protein that plays a central role in scavenging H2O2 in higher plants. The structure of stromal APX (sAPX) was determined at 1.6 Å to an R-factor of 19.1% and an R-free-factor of 22.3%. The electrostatic potential of the γ-channel that connects the molecular surface of sAPX to the γ-edge of heme was more positive than that of cytosolic APX (cAPX) from pea, so sAPX might bind more easily with ascorbate than cAPX. The overall structure of sAPX was similar to those of cAPX from pea and cytochrome c peroxidase (CCP) from yeast, with a substantial difference in a loop structure located in the vicinity of the heme. The side chain of Arg169 in sAPX corresponding to His169 in cAPX and His181 in CCP extended in the opposite direction from the heme, forming two hydrogen bonds with carbonyl groups in the loop structure. The rapid inactivation of sAPX might be due to the characteristic conformation of Arg169 owing to the loop structure of sAPX.
ISSN:0021-924X
DOI:10.1093/jb/mvg136