Budding yeast Gdt1 is a Golgi-localized calcium transporter required for stress-induced calcium signalling and protein glycosylation []. Its human homologue, TMEM165, may be a Golgi Ca2(+)/H(+) antiporter []. Defects in the human protein TMEM165 cause a subtype of Congenital Disorders of Glycosylation []. In Arabidopsis , this protein is variously known as CCHA1 (a chloroplast-localized potential Ca(2+)/H(+) antiporter), chloroplastic PAM71 (photosynthesis affected mutant 71), and GDT1-like protein 1, chloroplastic. It has been reported to be a putative chloroplast-localized Ca(2+)/H(+) antiporter with critical functions in the regulation of PSII and in chloroplast Ca(2+) and pH homeostasis []. It has also been suggested that it may function in Mn(2+) uptake into thylakoids, ensuring optimal PSII performance [].
