<p>Binding proteins are present both in gram-negative and gram-positive bacteria. They are the recognition components of the ABC transport systems that transport different nutrients into the cell, and are in some cases also involved in chemotaxis. In gram-negative bacteria, they are present in the periplasm between the inner and the porous outer membrane. Here, these highly specific proteins can bind to a certain ligand such as ions, sugars and amino acids. The protein-ligand complex can then interact with permeases bound to the inner membrane that transport the nutrient into the cell. Gram-positive bacteria lack an outer membrane and the binding protein must therefore be anchored to the cell membrane.</p><p>In this thesis different aspects of three members of the super-family of the periplasmic binding proteins have been studied. In the case of the allose-binding protein (ALBP) from <i>E. coli</i> we focused on the movement of the protein when ligand is bound and released. This protein was also compared with the ribose-binding protein (RBP) which belongs to the same structural cluster and from which both open and closed structures are available. The leucine-binding protein (LBP) from <i>E. coli</i> was studied with regards to the structural basis of its specificity for different ligands as well as its conformational changes. The leucine-isoleucine-valine protein has 80% sequence identity with LBP but still exhibits a different preference for ligands. The structure of the maltose-binding protein (MBP) was obtained from a gram-positive thermoacidophile, <i>A. acidocaldarius. </i>Here, our goal was to study acid-stability of proteins. Since little is known about this and structures of the mesophilic counterpart in <i>E. coli</i> are available, as well as structures from two hyperthermophiles, we had an opportunity to study differences in their structural properties that could explain their differing stabilities.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-3640 |
| Date | January 2003 |
| Creators | Magnusson, Ulrika |
| Publisher | Uppsala University, Department of Cell and Molecular Biology, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 899 |
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