Kinetic sedimentation of Rhizobium-aggregates produced by leguminous lectins

Abstract

Lectins from Canavalia brasiliensis (CnBr), Cratylia floribunda (CFL), Vatairea macrocarpa (VML) and Phaseolus vulgaris (PHA) aggregate Rhizobium bacteria. The relationship between specific sedimentation rate, m¢ (based on bacterial dry biomass) of bacterial aggregates and lectin concentrations was hyperbolic and showed bacterial surface affinity by lectins. R. tropici (Rt), R. leguminosarum bv. phaseoli (Rlp) and R. etli (Re) surfaces showed predominantly receptors of galactosidic nature. The Rt surfaces showed very high affinities (k s ¼ ±8.6 · 10 )8 ag lectin protein ml )1 ) by Gal-specific lectins (PHA and VML), and very low affinities (k s ¼ ±4.9 · 10 )6 ) by Glcspecific lectins (CnBr and CFL). The Rlp surface had intermediate affinities by lectins. The Re surface showed high affinities by PHA (k s ¼ ±1.26 · 10 )8 ) and intermediate affinities by VML, CnBr and CFL. The relationship between sedimentation specific m¢¢ (based on lectin weight) and bacterial density was a sigmoid and showed lectin affinity by Rt surfaces. The bacterial sedimentation showed positive cooperative binding of lectins. The V 00 max induced by Glc-specific lectins was ±20% of that produced by Gal-specific lectins. The PHA affinity (k s = 1.19 mg dry biomass ml )1 ) was larger than VML (k s = 1.23). The Glc-specific lectin affinities were smaller than those of Galspecific. The apparent binding site number of lectins (n app ) was: 2.7-PHA; 2.2-VML; 3.2-CFL and 3.2-CnBr. The dissociation constant, k s , of lectin-binding kinetics decreased with sugar-hapten treatment (10 lM). The n app decreased in PHA and CFL, increasing in VML + sugar-hapten treatment. This study showed that there is a difference in Rhizobium surfaces for lectin binding.

Detecção de inibidores de tripsina e atividade hemaglutinante em sementes de leguminosas arbóreas da amazônia

“…Isto ocorre porque, apesar de as espécies pertencerem à mesma família, a especificidade por carboidratos diverge para cada espécie, o que está diretamente relacionado à composição estrutural das proteínas e composição química dos eritrócitos, cujo padrão de glicosilação diferencia-se de acordo com a espécie e isto, conseqüentemente, implica se o extrato vegetal promoverá ou não a hemaglutinação, dependendo da ocorrência de lectinas (Moreira et al, 1990;Chrispeels et al, 1991;Martinez et al, 2005).…”

The interaction of and : net H efflux stimulus and alteration of extracellular Na concentration

“…At neutral pH, VML is predominantly a dimeric (70 kDa) protein, although tetramers (115 kDa) and larger aggregates (300 kDa) are present [2]. VML has been shown to bind specifically to the bacterial surfaces of Rhizobium tropici CIAT899 and R. etli USDA 9032 [3]. These two strains have been reported to induce nodule formation and fix atmospheric nitrogen in the roots of the legume Phaseolus vulgaris [4].…”

“…YM medium: 3.4 mM NaCl; 2.9 mM K 2 HPO 4 ; 6.6 mM MgSO 4 ; 10 À2 mM FeCl 3 ; 55 mM Mannitol; 1 g Yeast extract l À1 ; pH 6.8 2. MES-S buffer: 10 mM MES, 1 mM CaCl 2 , 1 mM MnCl 2 and 3 mM NaCl 3. S buffer: 1 mM CaCl 2 , 1 mM MnCl 2 and 3 mM NaCl.…”