Parkia platycephala lectin 2 was purified from Parkia platycephala (Leguminosae, Mimosoideae) seeds by affinity chromatography and RP-HPLC. Equilibrium sedimentation and MS showed that Parkia platycephala lectin 2 is a nonglycosylated monomeric protein of molecular mass 29 407 ± 15 Da, which contains six cysteine residues engaged in the formation of three intramolecular disulfide bonds. Parkia platycephala lectin 2 agglutinated rabbit erythrocytes, and this activity was specifically inhibited by N-acetylglucosamine. In addition, Parkia platycephala lectin 2 hydrolyzed b(1-4) glycosidic bonds linking 2-acetoamido-2-deoxy-b-d-glucopyranose units in chitin. The full-length amino acid sequence of Parkia platycephala lectin 2, determined by N-terminal sequencing and cDNA cloning, and its three-dimensional structure, established by X-ray crystallography at 1.75 Å resolution, showed that Parkia platycephala lectin 2 is homologous to endochitinases of the glycosyl hydrolase family 18, which share the (ba) 8 barrel topology harboring the catalytic residues Asp125, Glu127, and Tyr182.Abbreviations CTAB, cetyl triethylammonium bromide; GlcNac, N-acetyl-D-glucosamine; GSP, gene-specific forward primer; HPAEC-PAD, high-pH anion exchange chromatography with pulsed amperometric detection; PE, pyridylethylated; PPL1, Parkia platycephala lectin 1; PPL2, Parkia platycephala lectin 2; PTC, phenylisothiocyanate; PTH, phenylthiohydantoin.
A composição bioquímica elementar de sementes de seis cultivares de feijão de corda (Vigna unguiculata) foi determinada e a fração lipídica de cada cultivar, caracterizada. Os resultados sugerem que todas as farinhas de semente compartilham composição bioquímica similar, embora as cultivares Br-14 e CE-315 difiram das Br-9 e Br-17 no teor de umidade. As frações lipídicas purificadas foram caracterizadas quanto ao teor e tipos de ácidos graxos presentes. A cultivar Br-17 possui alto conteúdo de ácido palmítico (58,2%) e o menor conteúdo de ácido linoléico (6,4%) enquanto a Vita 7 apresenta alto conteúdo de ácido linoléico (21,8%) e relativamente baixo conteúdo de ácido palmítico (41%) em uma base comparativa. Os ácidos graxos pentacosanóico e eicosanóico representam a fração lipídica menor e o primeiro não ocorre em CE-315. Os resultados sugerem que diferentes cultivares obtidas por melhoramento genético podem apresentar diferenças quantitativas e qualitativas na composição bioquímica; assim, diferenças na capacidade germinativa, resistência a predadores no campo de plantio e no armazenamento, poderiam estar relacionadas à inibição ou estímulo da expressão de genes codificadores da síntese de moléculas relevantes, que refletem diferenças de composição, como demonstrado neste trabalho.
A chitin-binding protein named PPL-2 was purified from Parkia platycephala seeds and crystallized. Crystals belong to the orthorhombic space group P2 1 2 1 2 1 , with unit-cell parameters a = 55.19, b = 59.95, c = 76.60 Å , and grew over several days at 293 K using the hanging-drop method. Using synchrotron radiation, a complete structural data set was collected to 1.73 Å resolution. The preliminary crystal structure of PPL-2, determined by molecular replacement, presents a correlation coefficient of 0.558 and an R factor of 0.439. Crystallographic refinement is in progress.
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