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Abstract Detail

Hormone Biology

Campanella, James J. [1], Sigethy, Scott [1], Ludwig-Müller, Jutta [2].

A biochemical analysis of truncated auxin conjugate hydrolases in Medicago truncatula.

We have previously isolated and enzymatically characterized the auxin conjugate hydrolase family from the model legume Medicago truncatula (barrel clover). In the process of cloning the cDNA for the genes MtIAR31, -32, -33, -34, and -36, we also cloned a truncated version of MtIAR33 (Δ MtIAR33) which putatively expresses an alternative hydrolase protein from a secondary, internal AUG start site. We expressed this truncated protein in vitro, compared its enzymatic activity to the full-length protein, and found the activity and substrate recognition of the two differed. The full-length MtIAR33 had high activity against IAA-Aspartate (~1160 pmol auxin released/min/ml) with low activity against IBA-Alanine, while Δ MtIAR33 lost almost all activity against IAA-Aspartate, but gained increased activity against IBA-Alanine (~140 pmol auxin released/min/ml). These differences suggested a possible biological importance, so we constructed additional expression vectors containing versions of MtIAR31, -32, -34, and -36 that were each truncated at the same putative internal AUG start site found in ΔMtIAR33. Our goal has been to analyze each of these truncated hydrolases for substrate activity/specificity, as well as computer model the three-dimensional structures of the wild-type and truncated hydrolases along with their substrates to better understand which amino acids and structural peptide motifs are regulating the activity of these enzymes. Additionally, we will determine whether these alternative transcripts are actually expressed in vivo to form these truncated proteins.

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1 - Montclair State University, Biology and Molecular Biology, 1 Normal Avenue, Montclair, New Jersey, 07043, USA
2 - Technische Universität Dresden, Institut für Botanik, Dresden, Germany

auxin conjugate hydrolase
Medicago truncatula
truncated protein study
auxin regulation
protein conformation.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P35002
Abstract ID:73

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