New funding support into novel antimicrobial agent design and signalling processes
Two recently awarded grants to Professor Anthony Watts will help support work to gain deeper insights into membrane function using solid-state NMR.
Professor Watts is Director of the Biological Solid State Nuclear Magnetic Resonance (NMR) Centre at Rutherford Appleton Laboratories, and head of the Biomembrane Structure Unit in the Biochemistry Department. His group has one of the major solid-state NMR facilities in the world, with its high field (800MHz) wide bore magnet.
The plasma membrane, a 3-4nm lipid envelope that surrounds cells, is the outward-facing aspect of the cell – the site at which external stimuli control cell function and cells are targeted for destruction. Understanding how membranes function at the molecular level is still a major challenge in structural biology.
Solid-state NMR allows high resolution structural and functional details about membrane acting proteins to be determined (Click to enlarge)
Professor Watts uses the relatively new approach of solid-state NMR (ssNMR) to tackle this problem. Unlike many other direct structural approaches, ssNMR is able to provide high atomic resolution information, at the sub-angstrom level, about molecular interactions in large and complex systems, such as those found in membranes, whilst they are functionally active.
The Engineering and Physical Sciences Research Council grant, jointly funded by the National Physics Laboratory in Teddington as part of its “Length-scales in Biology” initiative, focuses on antimicrobial peptides (AMPs). AMPs associate with the bacterial membrane and kill bacteria in a variety of different way. They are emerging as new agents against bacterial infection as they invoke less bacterial resistance than conventional antibiotics.
Professor Watts will be studying the action of newly designed AMPs, which contain both natural and unnatural amino acids, to understand better the structural features that confer specific function and mechanism of action. The economic benefit of designing new AMPs, with specific targeting capacity, is very substantial.
The resolution of ssNMR will not only enable him to define the structural elements of the peptides precisely but also to characterise the extent of the membrane perturbation induced. The approach will be consolidated using Molecular Dynamics (MD) simulations to rationalise data.
'We will be designing, synthesising and labelling new peptides based on biologically available antimicrobial peptides, in a bottom-up approach, and then resolving structural and dynamic details that lead to membrane fusion and perturbation using solid state NMR,' says Professor Watts. 'Using the NMR, functional and MD data, we will be able to resolve generic features that can be used for novel antimicrobial action, for possible use in combating infection'.
Molecular dynamics simulation of a protein interacting with the membrane. Information obtained from solid-state NMR about such proteins can be included in molecular dynamics simulations (Click to enlarge)
The project will be highly multi-, cross- and trans-disciplinary, drawing on skills from chemical synthesis, biophysics, spectroscopy, computer-generated data, molecular biology and structural biology.
For the grant funded by the Medical Research Council, Professor Watts and his group will study one of a large group of proteins known as G-protein Coupled Receptors (GPCR). These are vital for mediating the signalling that occurs in the plasma membrane from external cues. About 70% of all known drugs are thought to modulate the activity of about 5% of known GPCRs, making the receptors one of the most important targets for drug development.
The GPCR that the Watts group works on is a target for Parkinson’s disease and dietary control. It has also recently been discovered as a marker in colon cancer and so is of potential interest in screening.
Professor Watts says that the benefits of using ssNMR methods for this type of work are that wild-type, functionally competent proteins in bilayers or membranes can be studied. He adds: 'We will specifically address the essential involvement of the flexible loops of membrane proteins, which link the membrane-embedded domains, in the activation and signalling process - something that is difficult to do using conventional structural methods and about which we know relatively little.'
Solid-state NMR was only developed in the mid-1990s for biological applications, and the Watts lab was one of the pioneers for this application. Although still a specialist approach, it is expected to add to and complement the wealth of information being generated by other methods. 'Our proximity to Diamond and the Wellcome membrane protein laboratory is a major benefit, since we are able to draw on their expertise, and are even carrying out NMR crystallography,' remarks Professor Watts. 'Eventually, it is hoped that solid state NMR will be one more routine tool in the structural biologists' arsenal.'