Research Accomplishment Reports 2010

Chloroplast-Localized Co- and Post-Translational Processing Enzymes: Essential Determinants of Protein Maturation

R.L. Houtz
Department of Horticulture

 

Non-Technical Summary

Co- and post-translational protein processing is often essential through influences on protein folding, stability, turnover, and activity. Additionally, it changes protein identity from that which can be deduced from DNA translation in unpredictable ways. Within the limited proteome of the chloroplast, a plethora of protein processing occurs, which, while recently physically characterized through newly developed techniques in mass spectroscopy polypeptide fingerprinting, have yet to be exploited through biochemical characterization of the associated enzymes, perhaps due to the inherent challenges therein.

The following studies capitalize on existing and previous accomplishments from the author's laboratory, widely recognized for discoveries in chloroplast-localized co- and post-translational protein processing. Application of these skills and abilities to the currently unknown areas of co- and post-translational processing enzymes in the chloroplast will provide information which allows prediction of protein processing and maturation in the chloroplast of all plants.

2010 Project Description

Activities - Experiments were conducted to evaluate the processivity of methylation in an important human SET-domain protein methyltransferase, SET 7/9. Additional experiments were conducted to evaluate the existence of a previously undiscovered protein methyltransferase responsible for the formation of trimethyllysine-115 in calmodulin. Two undergraduate students were mentored on research projects relative to these experiments.

Events - The results from studies of calmodulin methyltransferase were reported at the 2010 summer research conference on biological methylation sponsored by the Federation of the American Society for Experimental Biology.

Products - A provisional patent on the calmodulin methyltransferase was filed, United States Application 12/757,388.

2010 Impact

The genetic identity of the enzyme responsible for methylation of calmodulin was discovered. New techniques and procedures were developed to study and characterize the enzyme responsible for methylation of calmodulin.

2010 Publications

Magnani R, Dirk LM, Trievel RC, Houtz RL (2010) Calmodulin methyltransferase is an evolutionarily conserved enzyme that trimethylates Lys-115 in calmodulin. Nat Commun 1: 1-6.

Del Rizzo PA, Couture JF, Dirk LM, Strunk BS, Roiko MS, Brunzelle JS, Houtz RL, Trievel RC (2010) SET7/9 catalytic mutants reveal the role of active site water molecules in lysine multiple methylation. J Biol Chem 285: 31849-31858.

Whitney SM, Houtz RL, Alonso H (2010) Advancing our understanding and capacity to engineer nature's CO2 sequestering enzyme, Rubisco. Plant Physiol