Melittin

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Melittin
Melittin
Ribbon representation of the biologically active homotetramer

Existing structural data : 1bh1 , 2mlt

Mass / length primary structure 26 AS (monomer)
Secondary to quaternary structure Homotetramer
Precursor Propeptide (48 AA)
Identifier
Gene name (s) MELT
External IDs
Transporter classification
TCDB 1.C.18.1.1
designation Melittin family
Occurrence
Parent taxon Voices (Aculeata)

Melittin (from the Greek μέλιττα mélitta - the bee ) describes a cationic polypeptide that is contained in the bee venom as the main component (50-70%) and consists of 26 amino acids . Homologous peptides were found in other Stechimmen genera, including short-headed wasps ( Vespula ), hornets ( Vespa ) and field wasps of the genus Polistes . Melittin is a pore-forming toxin .

Structure and function

Ribbon and rod representation of the homodimer to illustrate the hydrophobic side chains.

The primary structure of the monomer consists of 26 amino acids ; it has a molecular mass of 2848  Da .

The structure is similar to that of a surfactant : 19 of the 20 amino acids at the N terminus are non-polar , the six amino acids at the C terminus of the protein are polar. Despite the predominant proportion of non-polar amino acids , it is soluble in water as a tetramer, i.e. four of the proteins each form a unit that is soluble in water.

Melittin is deposited in cell membranes and there forms channels that are permeable to dissolved ions . The permeability for anions is higher than that for cations . It is assumed that this occurs through a parallel arrangement of melittin in the cell membrane as a tetramer, that is, in contrast to the tetramer in water, all proteins point in the same direction.

The ion permeability of the cell membrane leads to the release of potassium ions and thus ultimately to cell death , mast cell disintegration and vasodilation .

Web links

Commons : Melittin  - collection of images, videos and audio files

Individual evidence

  1. ↑ Stanley D. Somerfield, Jean-Louis Stach et al .: Bee venom melittin blocks neutrophil O 2 - production. In: Inflammation , Vol. 10, No. 2, 1986, pp. 175-182 doi : 10.1007 / BF00915999 .
  2. ↑ Magdalena T. Tosteson, Daniel C. Tosteson: The sting. Melittin forms channels in lipid bilayers. In: Biophysical Journal , Vol. 36, No. 1, 1981, pp. 109-116, PMID 6269667 , PMC 1327579 (free full text).
  3. ↑ UniProt P59262
  4. ↑ UniProt P68409
  5. ↑ UniProt P59261
  6. ↑ Primary structure of the monomer: Gly - Ile - Gly - Ala - Val - Leu - Lys - Val - Leu - Thr - Thr - Gly - Leu - Pro - Ala - Leu - Ile - Ser - Trp - Ile - Lys - Arg - Lys - Arg - Gln - Gln
  7. ↑ UniProt P01501
  8. ^ A b Thomas C. Terwilliger, David Eisenberg: The Structure of Melittin. I. Structure determination and partial refinement. In: The Journal of Biological Chemistry. Vol. 257, No. 11, pp. 6010-6015, 1982, PMID 7076661 ( digitized ).
  9. ^ Horst Vogel, Fritz Jähnig: The structure of melittin in membranes. In: Biophysical Journal , Vol. 50, No. 4, 1986, pp. 573-582, PMID 3779000 ; PMC 1329835 (free full text).