We have generated nine monoclonal antibodies against subunits of the maize (Zea mays 1.) mitochondrial F1-ATPase. These monoclonal antibodies were generated by immunizing mice against maize mitochondrial fractions and randomly collecting useful hybridomas. To prove that these monoclonal antibodies were directed against ATPase subunits, we tested their cross-reactivity with purified F,-ATPase from pea cotyledon mitochondria. One of the antibodies (a-ATPaseD) cross-reacted with the pea F,-ATPase asubunit and two (8-ATPaseD and 8-ATPaseE) cross-reacted with the pea Fl-ATPase j3-subunit. This established that, of the nine antibodies, four react with the maize a-ATPase subunit and the other five react with the maize 8-ATPase subunit. Most of the monoclonal antibodies cross-react with the F1-ATPase from a wide range of plant species. Each of the four monoclonal antibodies raised against the a-subunit recognizes a different epitope. Of the five 8-subunit antibodies, at least three different epitopes are recognized. Direct incubation of the monoclonal antibodies with the F1-ATPase failed to inhibit the ATPase activity. lhe monoclonal antibodies a-ATPaseD and 8-ATPaseD were bound to epoxideglass QuantAffinity beads and incubated with a purified preparation of pea Fl-ATPase. lhe ATPase activity was not inhibited when the antibodies bound the ATPase. lhe antibodies were used to help map the pea F1-ATPase subunits on a two-dimensional map of whole pea cotyledon mitochondrial protein. In addition, the antibodies have revealed antigenic similarities between various isoforms observed for the a-and 8-subunits of the purified F1-ATPase. The specificity of these monoclonal antibodies, along with their cross-species recognition and their ability to bind the F1-ATPase without inhibiting enzymic function, makes these antibodies useful and invaluable tools for the further purification and characterization of plant mitochondrial F,-ATPases.Electrogenic H+-ATPases have been found in nearly a11 physiological membrane systems investigated. Each of these membrane-bound ATPases can be placed into one of severa1 groups. The three most common types of proton ATPases are E1-E2 type, Fo-F1 type, and the microsomal type (AlAwqati, 1986). The E1-E2 type ATPases are found in yeast and funga1 plasma membranes and the gastric plasma and microsomal membranes. ATPases of the microsomal type are located in the membranes of Golgi apparatus, ER, endosomes,

Extracts from either bean chloroplasts or etioplasts stimulate photophosphorylation in partially deficient chloroplast residues. Both extracts contain a latent Ca2+-dependent ATPase but the specific activity of the chloroplast extract is about sevenfold higher. The etioplast ATPase appears to have identical properties to a spinach chloroplast ATPase that has been shown to be a modified coupling factor for photophosphorylation.

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Purified pea (Pisum sativum) cotyledon Fl-ATPase contains six subunits rather than the five usually reported for F1-ATPases. The additional 26.5 kDa (a) subunit is shown by immunoblotting and N-terminal amino acid sequencing to be similar to bovine oligomycin-sensitivity-conferring protein (OSCP). It is concluded that the a subunit of plant mitochondrial Fl-ATPase is the plant OSCP. This OSCP subunit occurs in all mono-and di-cotyledonous species of plants tested (maize, oats, peas, potatoes, sweet potatoes and turnips).

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Extracts of bean (Phaseolus vulgaris L.) etioplasts and chloroplasts contain a dithiothreitol-activated Ca2+-dependent adenosine triphosphatase which is inhibited by . The chloroplast and etioplast enzymes have identical RF values upon disc gel electrophoresis. Optimum extraction of the enzyme from either plastid preparation is accomplished with 1 mM ethylenediamine tetraacetic acid. Photophosphorylation capacity can be partially restored to depleted chloroplast preparations by addition of either the chloroplast or etioplast extract. These results suggest that the adenosine triphosphatase from etioplasts and chloroplasts represents a modified coupling factor for photophosphorylation.The specific activity of the adenosine triphosphatase in the extracts of plastids increases upon greening of etiolated plants due to protein synthesis. This light-induced increase is inhibited by both chloramphenicol and cycloheximide, specific inhibitors of chloroplastic and cytoplasmic protein synthesis. There is no accumulation of adenosine triphosphatase in postribosomal supernatants of cycloheximide or chloramphenicol treated leaves. The results indicate that both the chloroplastic and the cytoplasmic ribosomal systems are required for the formation of the chloroplast adenosine triphosphatase.In the development of photosynthetic activity during the greening of bean leaves, photophosphorylation capacity increases in proportion to the increase of chlorophyll in the tissue (9). In terms of the plastid's ability to phosphorylate ADP, this could be interpreted in one of two ways. The etioplast may contain the enzymes or components necessary for phosphorylation but lack chlorophyll and possibly other electron transport carriers. Alternatively, the etioplasts may be deficient in components necessary for phosphorylation in addition to their lack of chlorophyll.A factor isolated from spinach chloroplasts that has latent ATPase activity has been shown to stimulate photophosphorylation in partially deficient chloroplast residues (28). Evidence suggests that this factor may be responsible for phosphorylation of ADP (23,28). In a previous paper (12) we have shown that extracts from bean etioplasts and chloroplasts contain a similar factor that stimulated photophosphorylation in I

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Plastids were isolated from 4- to 8-day-old seedlings of Gateway barley and its virescens mutant. At 4 days the normal barley plastids were well developed with respect to chlorophyll content, ultrastructure, and photoreductive activity. In contrast the mutant plastids were low in chlorophyll, contained predominantly single thylakoids, and their activity was low at this stage. By 8 days the amount of chlorophyll in the mutant plastids had increased, they had well-developed grana and their photoreductive activity reached normal levels. There seemed to be a correlation between the structure of photosynthetic membranes and their photoreductive activity during the development of the mutant barley plastids. It was concluded that chlorophyll content did not limit photoreductive activity at the earliest stage of development.