Association of carbonic anhydrase with a Calvin cycle enzyme complex in Nicotiana tabacum |
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Authors: | Judith A Jebanathirajah John R Coleman |
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Institution: | (1) Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada, CA |
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Abstract: | Chloroplast-localized carbonic anhydrase (CA; EC 4.2.1.1), an enzyme which catalyzes the reversible hydration of CO2, appears to be associated with other enzymes of the Calvin cycle in a large multienzyme complex. Gel-filtration fast protein
liquid chromatography (FPLC) of soluble proteins obtained by osmotic lysis of tobacco (Nicotiana tabacum L. cv. Carlson) chloroplasts results in the co-elution of a protein complex of greater than 600 kDa which includes CA, ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco), phosphoribulokinase (PRK), and ribose-5-phosphate isomerase. Anion-exchange FPLC of chloroplast
extracts indicates that there is an association of CA with other proteins that modifies its elution profile in a NaCl gradient,
and that Rubisco co-elutes with the fractions containing CA. Following a protocol described by Süss et al. (1993, Proc Natl
Acad Sci USA 90: 5514–5518), limited protease treatment of chloroplast extracts was used to show that the association of PRK
with other chloroplast proteins appears to protect a number of lysine and arginine residues which may be involved in specific
protein-protein interactions. A similar treatment of CA indicates some protection of these residues when CA is associated
with other chloroplast polypeptides but the level of protection is not as profound as that exhibited by PRK. In concert with
previously published immunolocalization studies, these data indicate that CA may be associated with Rubisco at the stromal
periphery of a Calvin cycle enzyme complex in which PRK is more centrally located and associated with thylakoid membranes.
Received: 2 June 1997 / Accepted: 28 June 1997 |
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Keywords: | : Calvin cycle Carbonic anhydrase Multienzyme complex Nicotiana (carbonic anhydrase) Ribulose-1 5-bisphosphate carboxylase/oxygenase |
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