PDBsum entry 2pt2

Metal transport

PDB id: 2pt2

Contents

Protein chain

316 a.a. *

Ligands

SO4 ×4

EDO

Metals

FE2

Waters ×318

* Residue conservation analysis

PDB id:

2pt2

Name:

Metal transport

Title:

Structure of futa1 with iron(ii)

Structure:

Iron transport protein. Chain: a. Engineered: yes

Source:

Synechocystis sp.. Organism_taxid: 1148. Strain: pcc 6803. Gene: futa1. Expressed in: escherichia coli. Expression_system_taxid: 562. Other_details: modified to contain an rtev cleavage site

Resolution:

2.00Å R-factor: 0.175 R-free: 0.212

Authors:

N.M.Koropatkin,A.M.Randich,M.Bhattachryya-Pakrasi,H.B.Pakrasi, T.J.Smith

Key ref:

N.Koropatkin et al. (2007). The structure of the iron-binding protein, FutA1, from Synechocystis 6803. J Biol Chem, 282, 27468-27477. PubMed id: 17626019 DOI: 10.1074/jbc.M704136200

Date:

07-May-07 Release date: 10-Jul-07

Protein chain

P72827  (FUTA1_SYNY3) -  Iron uptake protein A1 from Synechocystis sp. (strain ATCC 27184 / PCC 6803 / Kazusa)

Seq: 360 a.a.

Struc: 316 a.a.

DOI no: 10.1074/jbc.M704136200

J Biol Chem 282:27468-27477 (2007)

PubMed id: 17626019

The structure of the iron-binding protein, FutA1, from Synechocystis 6803.

N.Koropatkin, A.M.Randich, M.Bhattacharyya-Pakrasi, H.B.Pakrasi, T.J.Smith.

ABSTRACT

Cyanobacteria account for a significant percentage of aquatic primary productivity even in areas where the concentrations of essential micronutrients are extremely low. To better understand the mechanism of iron selectivity and transport, the structure of the solute binding domain of an ATP binding cassette iron transporter, FutA1, was determined in the presence and absence of iron. The iron ion is bound within the "C-clamp" structure via four tyrosine and one histidine residues. There are extensive interactions between these ligating residues and the rest of the protein such that the conformations of the side chains remain relatively unchanged as the iron is released by the opening of the metal binding cleft. This is in stark contrast to the zinc-binding protein, ZnuA, where the domains of the metal-binding protein remain relatively fixed, whereas the ligating residues rotate out of the binding pocket upon metal release. The rotation of the domains in FutA1 is facilitated by two flexible beta-strands running along the back of the protein that act like a hinge during domain motion. This motion may require relatively little energy since total contact area between the domains is the same whether the protein is in the open or closed conformation. Consistent with the pH dependence of iron binding, the main trigger for iron release is likely the histidine in the iron-binding site. Finally, neither FutA1 nor FutA2 binds iron as a siderophore complex or in the presence of anions, and both preferentially bind ferrous over ferric ions.

Selected figure(s)

Figure 2.
FIGURE 2. The iron-binding environment in FutA1. The top stereo figure shows the electron density of iron bound to FutA1 and some of the contact residues, and the bottom stereo figure shows some of the secondary shell contacts with the ligating residues. The orientation here is similar to that in Fig. 1 with the N-terminal domain toward the bottom of the figure and looking into the iron binding pocket.

Figure 4.
FIGURE 4. Changes in the iron-binding site upon iron release. In this stereo figure the ligating residues in the iron bound FutA1 structure are represented by the transparent stick figures, and the apo form is represented by the solid structure. The two structures were aligned according to the N-terminal domain using the program MolView X (34).

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 27468-27477) copyright 2007.

Figures were selected by the author.