A pH Switch Controls Zinc Binding in Tomato Copper-Zinc Superoxide Dismutase.
Biochemistry
; 60(20): 1597-1608, 2021 05 25.
Article
en En
| MEDLINE
| ID: mdl-33961402
ABSTRACT
Copper-zinc superoxide dismutase (SOD1) is a major antioxidant metalloenzyme that protects cells from oxidative damage by superoxide anions (O2-). Structural, biophysical, and other characteristics have in the past been compiled for mammalian SOD1s and for the highly homologous fungal and bovine SOD1s. Here, we characterize the biophysical properties of a plant SOD1 from tomato chloroplasts and present several of its crystal structures. The most unusual of these structures is a structure at low pH in which tSOD1 harbors zinc in the copper-binding site but contains no metal in the zinc-binding site. The side chain of D83, normally a zinc ligand, adopts an alternate rotameric conformation to form an unusual bidentate hydrogen bond with the side chain of D124, precluding metal binding in the zinc-binding site. This alternate conformation of D83 appears to be responsible for the previously observed pH-dependent loss of zinc from the zinc-binding site of SOD1. Titrations of cobalt into apo tSOD1 at a similar pH support the lack of an intact zinc-binding site. Further characterization of tSOD1 reveals that it is a weaker dimer relative to human SOD1 and that it can be activated in vivo through a copper chaperone for the SOD1-independent mechanism.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Superóxido Dismutasa
/
Solanum lycopersicum
Idioma:
En
Revista:
Biochemistry
Año:
2021
Tipo del documento:
Article
País de afiliación:
Estados Unidos