Download TWO GENES ENCODING FUNCTIONAL PECTIN

AtPMEI-1 AND AtPMEI-2: TWO GENES ENCODING FUNCTIONAL PECTIN
METHYLESTERASE INHIBITORS OF Arabidopsis thaliana
Alessandro Raiola1, Laura Camardella2, Alfonso Giovane3, Benedetta Mattei1 , Giulia De
Lorenzo1, Felice Cervone1, Daniela Bellincampi1
1
Dipartimento di Biologia Vegetale, Università di Roma “La Sapienza”, Piazzale Aldo Moro 5,
00185 Roma, Italy
2
Institute of Protein Biochemistry, CNR, Via Marconi 10, I-80125 Napoli, Italy
3
Department of Biochemistry and Biophysics, 2nd University of Naples, Via Costantinopoli 16, I80138 Napoli, Italy
A proteinaceous inhibitor of pectin methylesterase (PMEI) has been reported in kiwi but to
date no other proteins acting as PMEI have been found in plants.
Two sequences closely related to PMEI from kiwi were identified in Arabidopsis thaliana.
The corresponding cDNAs encode cell wall proteins of 173 and 176 amino acid residues
respectively. The sequences corresponding to the mature proteins were cloned and
expressed in a heterologous system. The purified proteins were characterized and shown
to be functional PMEIs. The inhibitory activity occurs through the formation of a 1:1
complex with tomato PME. Both proteins share with kiwi PMEI a predicted alpha-helix
structure and the conservation of four Cys residues involved in the formation of two
disulfide bridges as well as a fifth Cys residue bearing a free thiol group. The interaction
parameters of the two new inhibitors with PME purified from tomato fruits have been
studied .
We gratefully acknowledge funding from the Commission of the European Communities
contract QLK1-2000-00811 “Solving the Problem of Glycosidase Inhibitors in Food
Processing” and MIUR-COFIN.