PDBsum entry 1mpd

Periplasmic binding protein

PDB id: 1mpd

Contents

Protein chain

370 a.a.

Ligands

GLC-GLC

Waters ×492

References listed in PDB file

Key reference

Title

Crystal structures and solution conformations of a dominant-Negative mutant of escherichia coli maltose-Binding protein.

Authors

B.H.Shilton, H.A.Shuman, S.L.Mowbray.

Ref.

J Mol Biol, 1996, 264, 364-376. [DOI no: 10.1006/jmbi.1996.0646]

PubMed id

8951382

Abstract

A mutant of the periplasmic maltose-binding protein (MBP) with altered transport properties was studied. A change of residue 230 from tryptophan to arginine results in dominant-negative MBP: expression of this protein against a wild-type background causes inhibition of maltose transport. As part of an investigation of the mechanism of such inhibition, we have solved crystal structures of both unliganded and liganded mutant protein. In the closed, liganded conformation, the side-chain of R230 projects into a region of the surface of MBP that has been identified as important for transport while in the open form, the same side-chain takes on a different, and less ordered, conformation. The crystallographic work is supplemented with a small-angle X-ray scattering study that provides evidence that the solution conformation of unliganded mutant is similar to that of wild-type MBP. It is concluded that dominant-negative inhibition of maltose transport must result from the formation of a non-productive complex between liganded-bound mutant MBP and wild-type MalFGK2. A general kinetic framework for transport by either wild-type MalFGK2 or MBP-independent MalFGK2 is used to understand the effects of dominant-negative MBP molecules on both of these systems.

Figure 2.
Figure 2. Location of dominant- negative and suppressor mutation sites on the structure of closed, ligand-bound MBP; maltose is shown in a ball and stick represen- tation. Other regions in which mutations are known that affect transport (Treptow & Shuman, 1988; Hor & Shuman, 1993) are indicated by the shaded areas.

Figure 3.
Figure 3. Stereo drawings of the backbone of open (a) and closed (b) MBPW230R. Every 20th amino acid is labelled, as well as the N and C termini. Bound maltose and the side-chain of R230 are shown with ball-and-stick representations. In the case of the open conformation, the view with respect to the C-ter- minal domain is the same as that shown in Figure 2. For closed MBPW230R, the view is the same as (b) that shown in Figure 2.

The above figures are reprinted by permission from Elsevier: J Mol Biol (1996, 264, 364-376) copyright 1996.

Secondary reference #1

Title

Genetic analysis of periplasmic binding protein dependent transport in escherichia coli. Each lobe of maltose-Binding protein interacts with a different subunit of the malfgk2 membrane transport complex.

Authors

L.I.Hor, H.A.Shuman.

Ref.

J Mol Biol, 1993, 233, 659-670.

PubMed id

8411172