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Is dityrosine biosynthesis a possible drug target?

A Study of the importance of dityrosine in Aspergilli using a bioinformatic and molecular biological approach – is dityrosine biosynthesis a possible drug target?

The rising number of immunocompromised patients and high incidence of hospital acquired infections coupled with the impressive ability of microbes to acquire multiple resistance to antibiotics requires a more directed approach to the search for novel antibiotics than random screening. This has been made possible by the availability of complete genome sequences of many microorganisms allowing a drug-target directed approach.

The fellowship project combines the knowledge that a group of proteins: the Cytochrome P450s (CYP) are involved in important biosynthetic reactions and that inhibitors to some have been developed as commercially important drugs; e.g. the commonly used azole antifungal agents.  By using bioinformatics homology of CYP genes that have known function for cell survival and growth in one organism this may lead to the discovery of a potential drug target in another.

A CYP sequence found in Saccharomyces cerevisae that is involved in the biosynthesis of dityrosine a major component of the spore cell wall surface is CYP56 or DIT2.  A similar gene sequence has been identified in Aspergillus nidulans using bioinformatics and furthermore there is evidence of another gene with homology to DIT1 from S.cerevisae.  The fellowship project will start by confirming the presence of these homologous sequences in A.nidulans, cDNA of these genes in A.nidulans will be cloned into plasmids for transformation into a strain of S.cerevisae in which the native DIT1 and DIT2 genes have been ‘knocked out’.  If the A.nidulans genes are expressed in the transformed yeast and fulfil the same function then the yeast will still produce dityrosine.

The second half of the fellowship will involve checking for homologous genes in A.fumigatus the pathogenic organism which causes lung infections - aspergillosis; the protein of DIT2p will be modelled as a way of investigating potential drug- protein interaction and transcriptional analysis will provide insights in the timing of therapy with respect to the pathogen life cycle.

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