PMID: 25681186

Authors:

Acedo JZ, van Belkum MJ, Lohans CT, McKay RT, Miskolzie M, Vederas JC

Title:

Solution Structure of Acidocin B, a Circular Bacteriocin Produced by Lactobacillus acidophilus M46.

Journal:

Appl Environ Microbiol. 2015 Feb 13. pii: AEM.04265-14.

Abstract:

Acidocin B, a bacteriocin produced by Lactobacillus acidophilus M46, was originally reported to be a linear peptide composed of 59 amino acid residues. However, its high sequence similarity to gassericin A, a circular bacteriocin from Lactobacillus gasseri LA39, suggested that acidocin B might be circular as well. Acidocin B was purified from culture supernatant by a series of hydrophobic interaction chromatographic steps. Its circular nature was ascertained by MALDI-TOF mass spectrometry and MS/MS sequencing. The peptide sequence was found to consist of 58 amino acids with a molecular weight of 5,621.5 Da. The sequence of the acidocin B biosynthetic gene cluster was also determined and showed high nucleotide sequence similarity to that of gassericin A. The NMR solution structure of acidocin B in sodium dodecyl sulfate micelles was elucidated, revealing that it is composed of four alpha-helices of similar length that are folded to form a compact, globular bundle with a central pore. This is a three-dimensional structure for a member of subgroup ii circular bacteriocins, which are classified based on their isoelectric points of approximately 7 or lower. Comparison of acidocin B with carnocyclin A, a subgroup i circular bacteriocin with four alpha-helices and a pI of 10, revealed differences in the overall folding. The observed variations could be attributed to inherent diversity in their physical properties, which also required use of different solvent systems for 3D structural elucidation.