Proton and metal ion-dependent assembly of a model diiron protein

Citation
A. Pasternak et al., Proton and metal ion-dependent assembly of a model diiron protein, PROTEIN SCI, 10(5), 2001, pp. 958-969
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
PROTEIN SCIENCE
ISSN journal
0961-8368 → ACNP
Volume
10
Issue
5
Year of publication
2001
Pages
958 - 969
Database
ISI
SICI code
0961-8368(200105)10:5<958:PAMIAO>2.0.ZU;2-#
Abstract
DF1 is a small, idealized model for carboxylate-bridged diiron proteins. Th is protein was designed to form a dimeric four-helix bundle with a dimetal ion-binding site near the center of the structure, and its crystal structur e has confirmed that it adopts the intended conformation. However, the prot ein showed limited solubility in aqueous buffer, and access to its active s ite was blocked by two hydrophobic side chains. The sequence of DF1 has now been modified to provide a very soluble protein (DF2) that binds metal ion s in a rapid and reversible manner. Furthermore, the DF2 protein shows sign ificant ferroxidase activity, suggesting that its dimetal center is accessi ble to oxygen. The affinity of DF2 for various first-row divalent cations d eviates from the Irving-Willliams series, suggesting that its structure imp arts significant geometric preferences on the metal ion-binding site. Furth ermore, in the absence of metal ions, the protein folds into a dimer with c oncomitant binding of two protons. The uptake of two protons is expected if the structure of the ape-protein is similar to that of the crystal structu re of dizine DF1. Thus, this result suggests that the active site of DF2 is retained in the absence of metal ions.