Related Experiment Video
Updated: Jun 10, 2026

Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids
Published on: May 4, 2018
Discovery of Ribosomally Synthesized and Post-translationally Modified Knottins from the Deep-Sea Sponge Stryphnus
Lakmini N Kosgahakumbura1,2, Blazej Slazak1,3, Norelle L Daly4
1Pharmacognosy, Department of Pharmaceutical Biosciences, Biomedical Center, Uppsala University, Box 591, SE-751 24 Uppsala, Sweden.
Abstract:
Knottins are stable, structurally constrained mini-proteins with diverse bioactivities. This work presents the first report of a novel family of knottins, 'stryphnines', from the deep-sea sponge Stryphnus fortis. Peptidomic and transcriptomic analysis revealed a rich peptide repertoire and confirmed their ribosomal and sponge origin. This led to the isolation of two novel knottins containing a side-chain to side-chain ester linkage between serine 10/11 and glutamic acid 29/30, respectively, alongside one of their counterpart peptides devoid of the ester bond. The cryptic ester linkage was difficult to resolve due to β-elimination occurring at the serine side-chain ester. However, a combination of NMR, pH incubation studies, and MS/MS analysis facilitated their complete identification. Both stryphnines with and without the ester linkage exhibited no cytotoxicity and genotoxicity to mammalian cells. In contrast, stryphnines with the ester linkage strongly inhibited biofouling by barnacle larvae Amphibalanus improvisus and inhibited bacterial sialidase from Clostridium perfringens. The core knottin framework remained extremely stable in human serum at physiological conditions, despite ester bond hydrolysis occurring at high temperature and different pH treatments. The positive attributes of nontoxicity and biological stability, alongside demonstrated bioactivities, open up opportunities to further investigate the true ecological role and biosynthetic mechanisms of stryphnines.
Related Concept Videos
Ribosome Profiling
Applications of ribosome profiling
Ribosome profiling has many applications, including in vivo monitoring of translation inside a particular organ or tissue type and quantifying new protein synthesis levels.
The technique helps...
Riboswitches
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
Protein Modifications in the RER
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.
Ribosomal RNA Synthesis
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Ribosomal RNA Synthesis
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Directing Proteins to the Rough Endoplasmic Reticulum

