Evidence for self-association of a miniaturized version of agrin from hydrodynamic and small-angle X-ray scattering measurements

Interaction studies of a protein and carbohydrate system using an integrated approach: a case study of the miniagrin-heparin system

The major challenges in biophysical characterization of human protein-carbohydrate interactions are obtaining monodispersed preparations of human proteins that are often post-translationally modified and lack of detection of carbohydrates by traditional detection systems. Light scattering (dynamic and static) techniques offer detection of biomolecules and their complexes based on their size and shape, and do not rely on chromophore groups (such as aromatic amino acid sidechains). In this study, we utilized dynamic light scattering, analytical ultracentrifugation and small-angle X-ray scattering techniques to investigate the solution properties of a complex resulting from the interaction between a 15 kDa heparin preparation and miniagrin, a miniaturized version of agrin. Results from dynamic light scattering, sedimentation equilibrium, and sedimentation velocity experiments signify the formation of a monodisperse complex with 1:1 stoichiometry, and low-resolution structures derived from the small-angle X-ray scattering measurements implicate an extended conformation for a side-by-side miniagrin‒heparin complex.

Foreword to 'Quantitative and analytical relations in biochemistry'-a special issue in honour of Donald J. Winzor's 80th birthday

The purpose of this special issue is to honour Professor Donald J. Winzor's long career as a researcher and scientific mentor, and to celebrate the milestone of his 80th birthday. Throughout his career, Don has been renowned for his development of clever approximations to difficult quantitative relations governing a range of biophysical measurements. The theme of this special issue, 'Quantitative and analytical relations in biochemistry', was chosen to reflect this aspect of Don's scientific approach.

Recent advances in the analysis of macromolecular interactions using the matrix-free method of sedimentation in the analytical ultracentrifuge

Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or “hetero”-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10⁻¹² M to 10⁻¹ M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions.

Structural elucidation of full-length nidogen and the laminin-nidogen complex in solution

Nidogen-1 is a key basement membrane protein that is required for many biological activities. It is one of the central elements in organizing basal laminae including those in the skin, muscle, and the nervous system. The self-assembling extracellular matrix that also incorporates fibulins, fibronectin and integrins is clamped together by networks formed between nidogen, perlecan, laminin and collagen IV. To date, the full-length version of nidogen-1 has not been studied in detail in terms of its solution conformation and shape because of its susceptibility to proteolysis. In the current study, we have expressed and purified full-length nidogen-1 and have investigated its solution behavior using size-exclusion chromatography (SEC), dynamic light scattering (DLS) and small angle X-ray scattering (SAXS). The ab initio shape reconstruction of the complex between nidogen-1 and the laminin γ-1 short arm confirms that the interaction is mediated solely by the C-terminal domains: the rest of the domains of both proteins do not participate in complex formation.