1ZKB

Zinc-free Engineered maltose binding protein

Summary for 1ZKB

• Entry DOI: 10.2210/pdb1zkb/pdb
• Related: 1ziu 1zjl
• Descriptor: Maltose-binding periplasmic protein (2 entities in total)
• Functional Keywords: engineered maltose binding protein, zinc binding mutant, abc transport, sugar binding, metal binding protein
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 40712.10

Authors

Telmer, P.G.,Shilton, B.H. (deposition date: 2005-05-02, release date: 2005-12-20, Last modification date: 2023-08-23)

Primary citation

Telmer, P.G.,Shilton, B.H.
Structural studies of an engineered zinc biosensor reveal an unanticipated mode of zinc binding.
J.Mol.Biol., 354:829-840, 2005

PubMed Abstract: Protein engineering was used previously to convert maltose-binding protein (MBP) into a zinc biosensor. Zn(2+) binding by the engineered MBP was thought to require a large conformational change from "open" to "closed", similar to that observed when maltose is bound by the wild-type protein. We show that although this re-designed MBP molecule binds Zn(2+) with high affinity as previously reported, it does not adopt a closed conformation in solution as assessed by small-angle X-ray scattering. High-resolution crystallographic studies of the engineered Zn(2+)-binding MBP molecule demonstrate that Zn(2+) is coordinated by residues on the N-terminal lobe only, and therefore Zn(2+) binding does not require the protein to adopt a fully closed conformation. Additional crystallographic studies indicate that this unexpected Zn(2+) binding site can also coordinate Cu(2+) and Ni(2+) with only subtle changes in the overall conformation of the protein. This work illustrates that the energetic barrier to domain closure, which normally functions to maintain MBP in an open concentration in the absence of ligand, is not easily overcome by protein design. A comparison to the mechanism of maltose-induced domain rearrangement is discussed.

PubMed: 16288781
DOI: 10.1016/j.jmb.2005.10.016

Experimental method

X-RAY DIFFRACTION (2.2 Å)