Immunological cross-reactivity between proton-pumping inorganic pyrophosphatases of widely phylogenic separated species.

Immunological cross-reactivity among three types of inorganic pyrophosphatases, that is, the proton pumping inorganic pyrophosphate synthase (H(+)-PPi synthase) and the soluble inorganic pyrophosphatase, both from Rhodospirillum rubrum, and the vacuolar membrane inorganic pyrophosphatase (H(+)-PPase) from mung bean (Vigna radiata), were examined by means of immunoblot analyses. Antibodies raised against the mung bean H(+)-PPase cross-reacted with the H(+)-PPi synthase from R. rubrum but not with the soluble PPase from R. rubrum. N,N'-dicyclohexylcarbodiimide (DCCD), which inhibits both synthesis and hydrolysis of PPi catalysed by purified and chromatophore H(+)-PPi synthase, binds to the enzyme as shown by fluorography of [14C]DCCD labelling. These results suggest that the R. rubrum H(+)-PPase share close structural similarities with the vacuolar H(+)-PPase from Mung bean.