Gramicidin K, a new linear channel-forming gramicidin from Bacillus brevis

Abstract

A new gramicidin has been isolated from a commercial mixture of gramicidins A, B, and C. This new molecule, designated gramicidin K, contains formyl and ethanolamine blocking groups, has a molecular weight approximately 20% higher than gramicidin A, and is strongly retained on reversed-phase liquid chromatographic columns. Gramicidin K can be resolved into two components, one of which contains tyrosine. In lipid bilayer membranes, both components form channels of considerably longer lifetime and somewhat lower conductance than gramicidin A. Gramicidin K appears to be a lipopeptide that consists of a fatty acyl chain attached to the ethanolamine of gramicidin A.

Single channel and monolayer studies of acylated gramicidin A: influence of the length of the alkyl group

“…As expected on the basis of the results reported for gramicidin P, which differs from gramicidin A by the substitution of the ethanolamine group by methylamine (Trudelle et al 1987) and K (Koeppe et al 1985), all three acylated gramicidins give rise to single channel events. Although some differences, when compared to GA (Hladky and Haydon 1972) are noticed at the high salt concentrations (> 1 M) the general trend concerning the Ao-c relationship is the same (Ao is the conductance at zero applied potential and c the salt concentration) (Fig.…”

“…Although surprizing, it appears that the alcohol function has no effect on the conductance properties (Trudelle et al 1987) of the gramicidin molecule, and thus the functional role of the OH group is not clear. The recent isolation of gramicidin K (Koeppe et al 1985) from commercial gramicidin D suggests that this acylated gramicidin could be the biological precursor of gramicidin A. The fact that the presence of acyl groups on the C-terminus of other channel forming peptides, namely trichorzianines belonging to the peptaibol family, was also detected (Bodo, personal communication) supports this idea.…”

Molecular and channel-forming characteristics of gramicidin K's: a family of naturally occurring acylated gramicidins

“…Recently, gramicidin analogues containing a fatty acyl chain, most probably esterified to the ethanolamine hydroxyl group, were described (Koeppe et al, 1985). In this article we more fully characterize the structural and channel-forming properties of these acylated gramicidins.…”

“…Preliminary reports of some of this work have appeared (Koeppe et al, 1988;Williams et al, 1988). For the elution profile of the earlier fractions (nonacylated gramicidins C and A), see Figure 1 of Koeppe et al (1985).…”

Gramicidin Channels and Pores

“…Most experiments to date have been done on this six-component mixture, and it is referred to as gramicidin in this review. Gramicidin K, which has a fatty acid covalently attached to the ethanolamine residue, can also be isolated with gramicidin D in varying amounts in different preparations (62). A strain of Bacillus brevis also synthesizes gramicidin S (Soviet), a cyclic decapeptide (38) that fo rms ion carriers.…”