Dr John Crosby

Enzymes, Structure, Function and Analysis

e-mail john.crosby@bris.ac.uk

http://www.bris.ac.uk/Depts/Chemistry/staff/jcrosby.htm

Research in our group involves the use of a broad range of techniques including protein expression and purification, enzyme kinetics, and the accurate mass analysis of these large biomolecules by electrospray mass spectrometry. By isolating individual enzymes and establishing structural details, enzyme specificities, and kinetic characteristics we hope to understand fully how biosynthetic pathways are controlled.

Enzymology of Polyketide Biosynthesis

Many biologically active compounds are synthesised in nature via the polyketide pathway. The core of all polyketide structures is similar, and is assembled by a multicomponent enzyme system, the polyketide synthase (PKS). The synthase controls a series of cycles of reactions in which simple building blocks (usually acetate) are linked via carbon bond formation, followed by a highly specific sequence of modifying reactions. We aim to understand how the PKS controls the exact sequence of chemical steps involved in the biosynthesis of antibiotics. This will be achieved by isolating individual PKS components from a number of related bacterial systems, and establishing structural details, enzyme specificities, and kinetic characteristics. We will initially concentrate on the Streptomyces coelicolor system which produces actinorhodin (act) and examine the production of related novel compounds such as SEK4 and SEK4b.

UV Induced Immunosuppression

The skin is a vital and dynamic constituent of the immune system, forming a protective boundary between the body and the external environment. It has been known for many years that exposure of animals to UVB results in suppression of some cell-mediated immune responses. The mechanism of this immunosuppression has not been fully elucidated, but is likely to involve a complex series of events initiated in the skin, and resulting in immune dysregulation. Urocanic acid (UCA), a major ultraviolet-absorbing component of the stratum corneum, is one of the immunosuppressive mediators currently of interest. One research aim is to examine the co-operative relationship between immunosuppressive mediators.

References

Nature, 1999, 401, 502 J. Photochemistry Photobiology, 1999, 48, 42

Chem. Biol., 1998, 5, 35, 699 Acta Dermato-venereologica, 1999, 79, 426