title: Identification of a novel storage glycine-rich peptide from guava (Psidium guajava) seeds with activity against Gram-negative bacteria.
abstract: Bacterial pathogens cause an expressive negative impact worldwide on human health, with ever increasing treatment costs. A significant rise in resistance to commercial antibiotics has been observed in pathogenic bacteria responsible for urinary and gastro-intestinal infections. Towards the development of novel approaches to control such common infections, a number of defense peptides with antibacterial activities have been characterized. In this report, the peptide Pg-AMP1 was isolated from guava seeds (Psidium guajava) and purified using a Red-Sepharose Cl-6B affinity column followed by a reversed-phase HPLC (Vydac C18-TP). Pg-AMP1 showed no inhibitory activity against fungi, but resulted in a clear growth reduction in Klebsiella sp. and Proteus sp., which are the principal pathogens involved in urinary and gastro-intestinal hospital infections. SDS-PAGE and mass spectrometry (MALDI-ToF) characterized Pg-AMP1 a monomer with a molecular mass of 6029.34Da and small quantities of a homodimer. Amino acid sequencing revealed clear identity to the plant glycine-rich protein family, with Pg-AMP1 the first such protein with activity towards Gram-negative bacteria. Furthermore, Pg-AMP1 showed a 3D structural homology to an enterotoxin from Escherichia coli, and other antibacterial proteins, revealing that it might act by formation of a dimer. Pg-AMP1 shows potential, in a near future, to contribute to development of novel antibiotics from natural sources.
authors.affiliation: Centro de Análises Proteômicas e Bioquímicas, Programa de Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, Brasília-DF, Brazil.
authors.forename: Patricia B
authors.initials: PB
authors.lastname: Pelegrini
authors.forename: André M
authors.initials: AM
authors.lastname: Murad
authors.forename: Luciano P
authors.initials: LP
authors.lastname: Silva
authors.forename: Rachel C P
authors.initials: RC
authors.lastname: Dos Santos
authors.forename: Fabio T
authors.initials: FT
authors.lastname: Costa
authors.forename: Paula D
authors.initials: PD
authors.lastname: Tagliari
authors.forename: Carlos
authors.initials: C
authors.lastname: Bloch
authors.forename: Eliane F
authors.initials: EF
authors.lastname: Noronha
authors.forename: Robert N G
authors.initials: RN
authors.lastname: Miller
authors.forename: Octavio L
authors.initials: OL
authors.lastname: Franco
mesh_terms: D000595:Amino Acid Sequence; D000890:Anti-Infective Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D005998:Glycine / Q000737:chemistry*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D011487:Protein Conformation; D031647:Psidium / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry*; D016415:Sequence Alignment
chemical_list: D000890:Anti-Infective Agents; D010940:Plant Proteins; D005998:Glycine