PDBsum entry 2ft6

Electron transport

PDB id: 2ft6

Contents

Protein chain

122 a.a. *

Metals

_CU

Waters ×168

* Residue conservation analysis

PDB id:

2ft6

Name:

Electron transport

Title:

Structure of cu(ii)azurin with the metal-binding loop sequence "ctfpghsalm" replaced with "ctphpm"

Structure:

Azurin. Chain: a. Engineered: yes

Source:

Pseudomonas aeruginosa. Organism_taxid: 287. Gene: azu. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.25Å R-factor: 0.129 R-free: 0.155

Authors:

M.J.Banfield

Key ref:

C.Li et al. (2006). Basic requirements for a metal-binding site in a protein: the influence of loop shortening on the cupredoxin azurin. Proc Natl Acad Sci U S A, 103, 7258-7263. PubMed id: 16651527 DOI: 10.1073/pnas.0600774103

Date:

24-Jan-06 Release date: 11-Apr-06

Protein chain

P00282  (AZUR_PSEAE) -  Azurin from Pseudomonas aeruginosa (strain ATCC 15692 / DSM 22644 / CIP 104116 / JCM 14847 / LMG 12228 / 1C / PRS 101 / PAO1)

Seq: 148 a.a.

Struc: 122 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

DOI no: 10.1073/pnas.0600774103

Proc Natl Acad Sci U S A 103:7258-7263 (2006)

PubMed id: 16651527

Basic requirements for a metal-binding site in a protein: the influence of loop shortening on the cupredoxin azurin.

C.Li, S.Yanagisawa, B.M.Martins, A.Messerschmidt, M.J.Banfield, C.Dennison.

ABSTRACT

The main active-site loop of the copper-binding protein azurin (a cupredoxin) has been shortened from C(112)TFPGH(117)SALM(121) to C(112)TPH(115)PFM(118) (the native loop from the cupredoxin amicyanin) and also to C(112)TPH(115)PM(117). The Cu(II) site structure is almost unaffected by shortening, as is that of the Cu(I) center at alkaline pH in the variant with the C(112)TPH(115)PM(117) loop sequence. Subtle spectroscopic differences due to alterations in the spin density distribution at the Cu(II) site can be attributed mainly to changes in the hydrogen-bonding pattern. Electron transfer is almost unaffected by the introduction of the C(112)TPH(115)PFM(118) loop, but removal of the Phe residue has a sizable effect on reactivity, probably because of diminished homodimer formation. At mildly acidic pH values, the His-115 ligand protonates and dissociates from the cuprous ion, an effect that has a dramatic influence on the reactivity of cupredoxins. These studies demonstrate that the amicyanin loop adopts a conformation identical to that found in the native protein when introduced into azurin, that a shorter than naturally occurring C-terminal active-site loop can support a functional T1 copper site, that CTPHPM is the minimal loop length required for binding this ubiquitous electron transfer center, and that the length and sequence of a metal-binding loop regulates a range of structural and functional features of the active site of a metalloprotein.

Selected figure(s)

Figure 1.
Fig. 1. The structure of AZ, with the C-terminal ligand-containing loop and the copper ion shown in purple. The side chains of the Cys-112, His-117, and Met-121 ligands on this loop and also of His-46 are shown as stick models in purple. The backbone carbonyl oxygen of Gly-45, which provides the second weak axial interaction at the copper site, and the helical nature of the His-117-to-Met-121 sequence are omitted for clarity. The figure was prepared by using the program PYMOL (6).

Figure 4.
Fig. 4. Stereoview of active sites. (A) Overlay of the active sites of Cu(II) AZAMI (green), AZAMI-F (gray), AZ (purple), and AMI (yellow). The side chains of the coordinating residues and the amino acids on either side of the N-terminal His ligand are shown as stick models, copper atoms as spheres, and the backbone of the C-terminal ligand-containing loops as C^ traces. The residues are labeled as in AZ. (B) Overlay of the active sites of the Cu(I) form of AZAMI-F at pH 8 (slate) and pH 6 (cyan) is shown. The second conformation of the copper ion and His-115 at pH 6 are colored green. The figure was prepared by using the program PYMOL (6).

Figures were selected by the author.