Using a combination of solid-phase extraction, affinity chromatography, and analytical reversephase HPLC, a new linear peptide was isolated from dog-grass (Elytrigia repens) ears that does not contain cysteine residues. Identification of its primary structure by Edman automated degradation made it possible to reveal the presence of several polyglycine regions, each consisting of six to eight residues, between which short fragments consisting of polar amino-acid residues are localized. The C-terminal fragment of the molecule is a positively charged site enriched in arginine and histidine residues. The structural features of this peptide determine its functionality. Thus, checking the presence of antimicrobial properties in its recombinant analogue, obtained by heterologous expression in a prokaryotic system, made it possible to determine the MIC for the tested fungal cultures only at sufficiently high active concentrations (52–104 μM). However, this compound had regulatory properties: at a concentration of 25 μM, a reactivating effect was noted, which increased the level of survival of Saccharomyces cerevisiae to UV-irradiation. The data we obtained expand the understanding of the functional features of plant defense peptides of an unusual structural type.