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Pseudophomin
General info
| Original publication | Quail, 2002 |
| Original source | Pseudomonas fluorescens BRG100 |
| Other known sources (non-putative) | Pseudomonas sp. P867 (Reybroeck, 2014) |
| Stereochemistry determined by | X-ray crystallography: P. fluorescens BRG100 |
Chemical properties
| Molecular formula | C55H97N9O16 |
| Molecular weight | 1140.4 g/mol |
| Mono-isotopic mass | 1139.7053 Da (isobaric to other CLiPs, see text) |
| Solubility | n.a. |
| CMC | n.a. |
| Minimal surface tension | n.a. |
| 3D conformation | Crystal structure (Quail, 2002) |
| NMR data available in literature | DMF-d7 (Reybroeck, 2014) Acetone (Reybroeck, 2014) Methanol (Pedras, 2003) Acetone (Pedras, 2003) |
Introduction
Pseudophomins A and B were initially described in 2002 as bioactive agents against four fungal phytopathogens. (Pedras, 2003) In the same study, the chemical structure was determined by means of NMR spectroscopy and MS spectrometry. However, only the stereochemistry of L-Leu1 was determined by using γ-lactam formation. Shortly after, the crystal structures of both pseudophomin A and B were determined, thereby also elucidating their remaining stereochemical compositions. (Quail, 2002) Since then, pseudophomins have only been extracted from a single alternative source, being Pseudomonas sp. P867 isolated from milk of a Belgian farm. (Reybroeck, 2014)
Biological activity
Pseudophomin A and B display antifungal activities comparable to that of other viscosin group CLiPs such as WLIP and viscosinamide. (Pedras, 2003, Geudens, 2018) Moreover, they possess antagonistic activity against Gram-positive bacteria, but appear inactive against Gram-negatives. (Reybroeck, 2014) No information is available with respect to their activity against other microorganisms.
Chemical structure
The chemical structure of pseudophomin A was determined to be 3-OH C10:0 – L-Leu1 – D-Glu2 – D-aThr3 – D-aIle4 – D-Leu5 – D-Ser6 – L-Leu7 – D-Ser8 – L-Ile9 using NMR spectroscopy, MS spectrometry and X-ray crystallography. Using the same methodologies, it was found that pseudophomin B features an identical peptide part, while possessing a 3-OH C12:0 fatty acid tail. (Quail, 2002, Pedras, 2003)
Structurally, the pseudophomins belong to the viscosin group. It’s closed analogues are pseudodesmin A, which features a D-Val4 instead of D-allo-Ile4, and massetolide A, which differs only in the configuration of Leu5. Since the latter only differs in the stereochemistry of an amino acid, its brute formulae (C55H97N9O16) – and therefore, their molecular weights – are identical. They are isobaric and cannot be distinguished by mass spectrometric techniques alone.
Three-dimensional structure
The three-dimensional crystal structure of pseudophomin A consists of a fatty acid moiety linked to a left-handed alpha helix ranging between L-Leu1 and D-Ser6. From L-Leu7 onwards, the structure folds back on itself so to form an ester bond between the C-terminal carbonyl and the side chain alcohol moiety of D-aThr. The helix is therefore party endocyclic, and partly exocyclic. (Quail, 2002) This conformation is highly similar to that of other viscosin group CLiPs.
References
Geudens, et al. “Cyclic lipodepsipeptides from Pseudomonas spp. – Biological Swiss-Army Knives.” Frontiers in Microbiology9, 1867 (2018):
https://dx.doi.org/10.3389/fmicb.2018.01867.
Pedras, et al. “Structure, chemistry, and biological activity of pseudophomins A and B, new cyclic lipodepsipeptides isolated from the biocontrol bacterium Pseudomonas fluorescens.” Phytochemistry62, 7 (2003): https://dx.doi.org/10.1016/s0031-9422(02)00617-9.
Quail, et al. “Pseudophomins A and B, a class of cyclic lipodepsipeptides isolated from a Pseudomonas species.” Acta Crystallographica Section C58, 5 (2002).
Reybroeck, et al. “Cyclic lipodepsipeptides produced by Pseudomonas spp. naturally present in raw milk induce inhibitory effect on microbial inhibitor assays for antibiotic residue screening.” PLoS One9, 5 (2014): https://dx.doi.org/10.1371/journal.