Glycine-Containing Flaxseed Orbitides

Abstract

Five new orbitides, cyclolinopeptides 21-25, were identified in flaxseed oil (Linum usitatissimum) extracts. Their HPLC-ESIMS quasimolecular ion peaks at m/z 1097.7 (21), 1115.6 (22), 1131.6 (23), 1018.6 (24), and 1034.6 (25) [M + H](+) corresponded to the molecular formulae C59H89N10O10, C58H87N10O10S, C58H87N10O11S, C53H80N9O9S, and C53H80N9O10S, respectively. Their structures were elucidated by extensive HPLC-ESIMS/MS analyses, and their presence was confirmed by precursor proteins identified in flax genomic DNA sequence data. The amino acid sequences of these orbitides were confirmed as [1-10-NαC]-GILVPPFFLI, [1-10-NαC]-GMLIPPFFVI, [1-10-NαC]-GOLIPPFFVI, [1-9-NαC]-GMLVFPLFI, and [1-9-NαC]-GOLVFPLFI for cyclolinopeptides 21-25, respectively. Previously reported orbitides, [1-9-NαC]-ILVPPFFLI (1), [1-9-NαC]-MLIPPFFVI (2), [1-9-NαC]-OLIPPFFVI (3), [1-8-NαC]-MLVFPLFI (7), and [1-8-NαC]-OLVFPLFI (8), were also present in flaxseed oil. The precursors of orbitides 21, 22, and 24 also produced orbitides 1, 2, and 7 by alternative cyclization. Cyclolinopeptides 3, 8, 23, and 25 contain MetO (O) and are not directly encoded, but are products of post-translational modification of the Met present in 2, 7, 22, and 24, respectively. Sufficient cyclolinopeptide 23 was isolated for characterization via 1D ((1)H and (13)C) and 2D (NOESY and HMBC) NMR spectroscopy. These compounds have been named as cyclolinopeptides U, V, W, X, and Y for 21, 22, 23, 24, and 25, respectively.

Affinity binding of chicken apolipoprotein A1 to a novel flax orbitide (linusorb)

“…LOs containing an amine side chain, 8 and 10, was synthesized from 2 and 5 as described in our previous work. 36 9 and 11 were prepared using methods modied from a published procedure. 37 8 (0.16 g, 0.14 mmol) was dissolved in MeOH (5 mL) and triethylamine (0.5 mL) was added to the solution.…”

“…LOs discovered thus far have eight to ten amino acids. [4][5][6][7][8][9] The selected structures of LOs 1-7 were shown in Fig. 1A.…”

“…Elemental analysis of blank and LO gels (9 and 11)Affi-gel coupled peptide(9) was slurry packed into a empty preparative column [POROS PI 20 mm column (4.6 Â 100 mm, 1.7 mL), Applied Biosystems]. The packed column was connected to an Agilent 1200 series HPLC system equipped with a quaternary pump, autosampler, degasser and diode array detector (Agilent G1315C/D, 1024-element photodiode array, wavelength range 190-300 nm).…”

A family of small, cyclic peptides buried in preproalbumin since the Eocene epoch

“…In Linum usitatissimum (Linaceae), the genes encoding the cyclolinopeptides contain multiple copies of a single orbitide sequence or closely related sequences (Burnett, Jadhav, Okinyo‐Owiti, Poth, & Reaney, ; Covello et al., ; Okinyo‐Owiti et al., ), whereas orbitide genes in the Caryophyllaceae and Rutaceae are short and encode only a single peptide (Condie et al., ; Covello et al., ). The PLPs differ from these in that their sequences are buried within genes that also code for a completely unrelated protein, namely a napin‐type seed storage albumin.…”

Metal binding novel flaxseed peptides (linusorbs)

“…However, in fresh flaxseed and flaxseed oil, the MetO concentrations are low, but LO with MetO (2 and 3) accumulate in flaxseed oil with storage (Br€ uhl et al, 2007). Based on flax genomic DNA sequences, new LOs are likely to be identified as DNA and mRNA appear to encode additional precursor proteins (Burnett et al, 2015). Previous studies show that peptides can bind metals, LO 6 interacts and weakly complexes with Tb 3+ with the metal ion positioned proximally to a Phe residue (Chatterji et al, 1987).…”