In situ photoreactions of proteins in spectrometers leading to variations in signal intensities

Balasubramanian, D.; Guptasarma, Purnananda; Luthra, Manni

doi:10.1021/ja00031a050

Cited by 5 publications

(1 citation statement)

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“…This is because photooxidation of this tryptophan has been shown to decrease lytic activity in melittin . The use of tryptophan fluorescence in these experiments would have been further complicated by the low quantum yield of tryptophan residues and formation of fluorescent byproducts on tryptophan photooxidation, , which might have introduced artifacts in data acquisition and interpretation.…”

Section: Resultsmentioning

confidence: 99%

Lipid Headgroup Charge Controls Melittin Oligomerization in Membranes: Implications in Membrane Lysis

2021

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Melittin, a hemolytic peptide present in bee venom, represents one of the most well-studied amphipathic antimicrobial peptides, particularly in terms of its membrane interaction and activity. Nevertheless, no consensus exists on the oligomeric state of membrane-bound melittin. We previously reported on the differential microenvironments experienced by melittin in zwitterionic and negatively charged phospholipid membranes. In this work, we explore the role of negatively charged lipids in the oligomerization of membrane-bound melittin (labeled with 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD)) utilizing a quantitative photobleaching homo-FRET assay. Our results show that the presence of negatively charged lipids decreases melittin oligomeric size to ∼50% of that observed in zwitterionic membranes. This is possibly due to differential energetics of binding of the peptide monomer to membranes of different compositions and could explain the reduced lytic activity yet tighter binding of melittin in negatively charged membranes. These results constitute one of the first experimental observations on the role of phospholipid headgroup charge in the oligomerization of melittin in membranes and is relevant in light of previous apparently contradictory reports on oligomerization of membrane-bound melittin. Our results highlight the synergistic interplay of peptide-membrane binding events and peptide oligomerization in modulating the organization, dynamics, and function of amphipathic α-helical peptides.

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Section: Resultsmentioning

confidence: 99%