A 15-residue peptide with alternating L- and D-amino acids whose dimers form textbook ion channels.
Also known as: gramicidin D · gramicidin A
Part of the Foundational & therapeutic peptides cluster
Overview
Gramicidin is a 15-residue linear peptide antibiotic from the soil bacterium Brevibacillus brevis, notable for alternating L- and D-amino acids. Two molecules assemble head-to-head into a beta-helical channel that lets monovalent cations flood across bacterial membranes, collapsing their ion gradients. It is used topically, often with polymyxin B or neomycin. This page is educational and not medical advice.
Source & context
Biological / chemical source: Soil bacterium Brevibacillus brevis (formerly Bacillus brevis)
Primary research or clinical context: Topical antibiotic (approved for external use) and a classic ion-channel model
Channel-forming mechanism
Gramicidin's alternating L/D sequence lets it fold into a single-stranded beta-helix; two such helices join end-to-end to span the membrane. The resulting pore conducts Na+, K+ and H+, dissipating the electrochemical gradients bacteria need to survive. This makes it a foundational model system in ion-channel biophysics.
Clinical use
Because it is toxic if absorbed systemically, gramicidin is limited to topical products such as antibiotic eye drops, throat lozenges and skin ointments, frequently combined with polymyxin B and neomycin. Selective toxicity toward bacteria at low concentrations underlies these external formulations.
FAQ about Gramicidin
What is Gramicidin?+
Gramicidin is a 15-residue linear peptide antibiotic from the soil bacterium Brevibacillus brevis, notable for alternating L- and D-amino acids. Two molecules assemble head-to-head into a beta-helical channel that lets monovalent cations flood across bacterial membranes, collapsing their ion gradients. It is used topically, often with polymyxin B or neomycin. This page is educational and not medical advice.
Is Gramicidin an approved medicine?+
Gramicidin: Topical antibiotic (approved for external use) and a classic ion-channel model. Always follow licensed medical guidance for approved products.
What is the typical length of Gramicidin?+
Gramicidin is commonly described as approximately 15 amino acids (Linear peptide antibiotic (ion-channel former)).