The chloroplastic 2-oxoglutarate/malate transporter has dual function as the malate valve and in carbon/nitrogen metabolism.
Kinoshita H, Nagasaki J, Yoshikawa N, Yamamoto A, Takito S, Kawasaki M, Sugiyama T, Miyake H, Weber APM, Taniguchi M. Plant J. 2011 Jan; 65(1):15-26. Epub 2010 Nov 15.