Characterization of Vacuolar H+-Atpases that are Sensitive and Tolerant to Cold
The susceptibility of the vacuolar H+-ATPase to cold in vivo differed markedly between leguminous species sensitive and tolerant to cold. In chilling-sensitive species such as mung bean (Vigna radiata L.), the vacuolar H+-ATPase exhibited a marked decline in activity during the early process of cold treatment. In chilling-tolerant species such as pea (Pisum sativm L.), by contrast, the H+-ATPase remained to be highly active for long periods of cold treatment. The obvious difference in the cold susceptibility of the vacuolar H+-AT-Pases in vivo between the two species was also reflected in the sensitivity to the MgATP-de-pendent cold inactivation in vitro, in particular, with respect to the sensitivity to chaotropic anions, such as Cl−, NO2 −, and NO3 −. The H+-ATPase from chilling-sensitive species is more susceptible to the anions, especially to the NO2 −, than the enzyme from chilling-tolerant species. The vacuolar H+-ATPases were categorized into two types, namely, the cold-sensitive “mung bean-type” and the cold-stable “pea-type” enzymes, in terms of the susceptibility to the MgATP-dependent cold inactivation in the presence of NO2 − ions. Immunoblot analyses using anti-mung bean H+-ATPase antibodies have revealed that the antigenicity of the 16 kD proteolipids is distinctly different between the two types of enzyme.
KeywordsCold Treatment Mung Bean Vacuolar Membrane Azuki Bean Cold Sensitivity
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