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UNDERSTANDING THE MECHANISM OF ACTION OF THE PLASMODIUM FALCIPARUM LARIAT
DEBRANCHING ENZYME IN THE INTRON TURNOVER PATHWAY
Maria Daleke, Kevin Karplus
University of California Santa Cruz
14/02/05
More and more information is gained on pre-mRNA splicing mechanisms, but little is known
about the biological and evolutionary significance of introns. We therefore need a simple way
of investigating those, and the enzymes involved in the intron turnover pathway. The target
enzyme of the study, the RNA lariat debranching enzyme (DBR) from mosquito-borne
parasitic protozoan Plasmodium falciparum, participates in the early degradation of introns in
lariat conformation by debranching them to enable further degradation by exonucleases. The
short term aim is to develop an assay for expressing the enzyme in bacteria, and for
expressing the two subunits that build up the protein separately. Thereafter site-directed
mutagenesis will be performed based on structural predictions using bioinformatics tools, as
no experimental structure determination has been performed on DBR proteins, to examine the
functions of the two subunits, and to understand the mechanism of action of the protein.
It has been shown in Schizosaccharomyces pombe that intron accumulation
cause severe growth effects, and it has been suggested that lariat debranching is a rate-limiting
step in the breakdown of introns. This makes the lariat DBR protein a suitable drug target, and
by using the P. falciparum DBR enzyme the long term goal of finding a treatment for malaria,
a disease that kills 2.7 million people and infects 300 – 500 million people annually, may be
fulfilled.