Diptericin

Diptericin is a small antimicrobial peptide produced by insects as part of their innate immune system. In Drosophila melanogaster, it is one of the major humoral effectors induced in response to infection, especially by Gram-negative bacteria.

Gene and expression: Diptericin is encoded by the Dpt gene. It is primarily expressed in the fat body and released into the hemolymph as part of the systemic immune response. Its transcription is strongly regulated by immune signaling pathways, with the IMD pathway driving its induction in response to Gram-negative bacterial components such as peptidoglycan; other antimicrobial peptides are governed by different pathways, such as Toll.

Structure and processing: Diptericin is produced as a precursor containing a signal peptide and a pro-region, which is processed to yield the mature, active peptide after secretion.

Activity and mechanism: The mature peptide is cationic and tends to act against Gram-negative bacteria. It likely interacts with bacterial membranes or outer membrane components, leading to membrane disruption and bacterial death. Its activity is generally more potent against Gram-negative organisms such as Escherichia coli and related Enterobacteriaceae, with limited to no activity against many Gram-positive bacteria.

Spectrum and limitations: Diptericin demonstrates a narrow spectrum focused on Gram-negative bacteria. Its effectiveness can be influenced by bacterial cell envelope structures and environmental conditions, and it functions as part of a broader repertoire of antimicrobial peptides in insects.

Significance: As a well-studied example of insect antimicrobial peptides, Diptericin provides insight into innate immune regulation, peptide maturation, and host–pathogen interactions in Diptera. It is frequently used as a molecular marker for IMD pathway activity in research.