Eukaryotic proteins are modified
extensively both co- and post-translationally. There are as many as two hundred
separate types of modifications that can occur throughout the polypeptide
chain. The N-terminal region is a particularly active area for such
alterations. N-terminal modifying enzymes (NTMEs) catalyze the co- and post-
translational cleavage of amino acids from the N-terminus of many proteins. These
modifications have been implicated with the control of protein fate (i.e.
activation, regulation, localization, half-life, etc.). In collaboration with
Dr. Linda Walling and Dr. Ralph Bradshaw, we aim to examine and understand the
role of the principal enzymes expected to be involved in N-terminal processing
of the Arabidopsis thaliana proteome. This area of study is still in its
infancy.
Understanding the specificity of an
NTME is essential for identifying its potential targets in vivo. We assess
the substrate specificity of 3 of the NTMEs of the Arabidopsis thaliana –
leucyl aminopeptidase 1 (AtLAP1) and aspartic aminopeptidases 1 and 2 (DAP1,
DAP2) – through combinatorial peptide library analysis. Our analysis will extend to the other NTMEs
from A. thaliana, which our collaborator Dr.Linda Waling will kindly provide to
us. These studies will determine the extended specificities of each NMTEs,
which are not established in any organism.
Working on this project: Roxana Coman – graduate student
Alexander Godoy – undergraduate student
2. SUBTRATE SPECIFICITY OF CARDOSIN A BY COMBINATORIAL
PEPTIDE LIBRARY ANALYSIS
Many plant aspartic proteases share structural and
functional characteristics with their mammalian and microbial
counterparts. Cardosin A is an aspartic
protease found within the flowers of cardoon, and it is thought to be involved
in cell death events, particularly in response to stress. Our lab works with the Faro laboratory from
Portugal to determine active site amino acid specificity for this enzyme in
order to better understand how proteases bind and cleave substrates.
