Two different late embryogenesis abundant proteins from Arabidopsis thaliana contain specific domains that inhibit Escherichia coli growth Francisco Campos a , Fernando Zamudio b , Alejandra A. Covarrubias a, * a Departamento de Biologı ´a Molecular de Plantas, Instituto de Biotecnologı ´a, Universidad Nacional Auto ´noma de Me ´ xico, Av. Universidad 2001, Cuernavaca, Morelos 62210, Mexico b Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnologı ´a, Universidad Nacional Auto ´noma de Me ´ xico, Av. Universidad 2001, Cuernavaca, Morelos 62210, Mexico Received 10 January 2006 Available online 7 February 2006 Abstract Late embryogenesis abundant (LEA) proteins constitute a set of proteins widespread in the plant kingdom that show common phys- icochemical properties such as high hydrophilicity and high content of small amino acid residues such as glycine, alanine, and serine. Typically, these proteins accumulate in response to water deficit conditions imposed by the environment or during plant normal devel- opment. In this work, we show that the over-expression in Escherichia coli of proteins of the LEA 2 and the LEA 4 families from Arabidopsis thaliana leads to inhibition of bacterial growth and that this effect is dependent on discrete regions of the proteins. Our data indicate that their antimicrobial effect is achieved through their interaction with intracellular targets. The relevance of the cationic nature and the predicted structural organization of particular protein domains in this detrimental effect on the bacteria growth process is discussed. Ó 2006 Elsevier Inc. All rights reserved. Keywords: LEA proteins; Hydrophilins; Antimicrobial; Cationic proteins; Growth inhibition; Protein expression Late embryogenesis abundant (LEA) proteins were ini- tially identified in the late stage of seed maturation in cot- ton and wheat [1]. LEA proteins have been detected in angiosperms, gymnosperms, lower plants, and algae [2–4], suggesting that they may be ubiquitous in the Plantae king- dom. Furthermore, LEA-like proteins have been detected in nematodes [5,6] and bacteria [7,8,10,11]. Five groups of typical LEA proteins have been described on the basis of similarities in their amino acid sequence and conserved motifs [3,9,10]. Typical LEA pro- teins are highly hydrophilic, present a high percentage of glycine or other small amino acids (ala, ser, and thr), and lack or present low content of tryptophan and cysteine res- idues. These general characteristics led to the identification of a wide group of proteins, present in different organisms, termed hydrophilins, in which many LEA proteins are included [11]. It has been suggested, and for some it has been shown, that these proteins have little or no ordered secondary structure [12–16]. LEA proteins also accumulate in vegetative tissues in response to water deficit [3,17,18]. Based on their bio- chemical and physicochemical properties and on their expression patterns, it has been suggested that these pro- teins function as protectors of cellular and/or macromo- lecular structures or as detoxifying molecules to alleviate the increase in ion concentration during water limiting conditions [11,19–21]. To further extend our tools to study the properties of these proteins, we have over-expressed the so-called typi- cal-LEA proteins from Arabidopsis thaliana in Escherichia coli. In this work, we report that the over-expression of proteins of the LEA2 (ERD10; 22) and the LEA4 [23] fam- ilies from A. thaliana has an inhibitory effect on the growth of E. coli and that this effect is dependent on discrete regions present in these proteins. 0006-291X/$ - see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2006.01.151 * Corresponding author. Fax: +52 777 313 9988. E-mail address: crobles@ibt.unam.mx (A.A. Covarrubias). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 342 (2006) 406–413 BBRC