Acanthoscurrin: a novel glycine-rich antimicrobial peptide constitutively expressed in the hemocytes of the spider Acanthoscurria gomesiana.

We report the isolation of a novel antimicrobial peptide, acanthoscurrin, from the hemocytes of unchallenged tarantula spider Acanthoscurria gomesiana. A combination of Edman degradation, mass spectrometry and cDNA cloning revealed the presence of two isoforms of acanthoscurrin, differing by two glycine residues. Both displayed cationic properties and a high percentage of glycine residues. However, acanthoscurrins have no structural similarities with already known glycine-rich antimicrobial peptides from animals and plants. As deduced from cDNA cloning and mass spectrometry, the amino acid sequence of acanthoscurrin begins with a putative signal peptide of 23 amino acids followed by the mature peptide, which is post-translationally modified by a C-terminal amidation. Acanthoscurrins are constitutively expressed in hemocytes and released to plasma following an immune challenge.