Related Experiment Video
Updated: Aug 4, 2026
12:27
Measuring Peptide Translocation into Large Unilamellar Vesicles
Published on: January 27, 2012
Sequence requirements for the activity of membrane-active peptides
J A Werkmeister1, D R Hewish, A Kirkpatrick
1CSIRO Molecular Science, Parkville Laboratory, Vic 3052, Australia.
Summary
Synthetic peptides mimicking melittin show potent hemolytic and cytolytic activity. Activity depends on positive charge, with modifications allowing for controlled activation and enhanced potency.
Area of Science:
- Biochemistry
- Peptide Chemistry
Background:
- Melittin, a major component of bee venom, exhibits significant hemolytic and cytolytic properties.
- Understanding the structure-activity relationship of melittin is crucial for developing novel therapeutic agents.
Purpose of the Study:
- To synthesize and characterize novel peptides based on the melittin sequence.
- To investigate the role of specific residues and charge distribution in hemolytic and cytolytic activity.
- To explore strategies for modulating peptide activity, including inactivation and activation.
Main Methods:
- Synthesis of synthetic peptides with variations in the C-terminal amide and N-terminal modifications.
- Assay of hemolytic and cytolytic activity of synthesized peptides.
- Analysis of structure-activity relationships based on charge and sequence modifications.
Main Results:
- Synthetic peptides demonstrated melittin-like hemolytic and cytolytic activity, contingent on charge constraints.
- At least two positive charges, including the N-terminal amine, were essential for activity.
- N-terminal acetylation or non-acidic presequences inactivated peptides, while protease-cleavable sequences allowed for activation.
- Peptides with additional positive charges on the hydrophilic face exhibited enhanced activity.
Conclusions:
- The C-terminal residue and overall charge distribution are critical determinants of melittin peptide activity.
- Strategies for N-terminal modification can control peptide inactivation and activation via proteolysis.
- Designed peptides can surpass melittin's hemolytic activity, offering potential for targeted applications.
Related Concept Videos
01:41Signal Sequences and Sorting Receptors
Signal sequences are short amino acid sequences that guide newly synthesized proteins to their proper location within the cell. Classical signal sequences are fifteen to sixty amino acids long and present at the N-terminus of a polypeptide chain. Each signal sequence has a conserved segment of basic residues towards their N terminus, a hydrophobic core, and a C-terminus rich in polar residues. The C-terminus also contains a signal cleavage site and features a -3 -1 sequence motif. The -3-1...
01:39Mitochondrial Precursor Proteins
Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70 chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Most of the mitochondrial precursors...
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:26Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
01:29Insertion of Multi-pass Transmembrane Proteins in the RER
The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
01:27Post-translational Translocation of Proteins to the RER
A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...