Expression and subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in light-grown Euglena gracilis and three nonchlorophyllous cell lines.

Abstract

The expression and subcellular location of porphobilinogen deaminase (PBGD, also known as hydroxymethylbilane synthase; EC 4.3

Structure and Expression of Chloroplast-Localized Porphobilinogen Deaminase from Pea (Pisum sativum L.) Isolated by Redundant Polymerase Chain Reaction

“…This value increases to 60% if conservatively substituted residues are included. It is interesting that, although the enzymes in both Euglena (Shashidhara and Smith, 1991;Shashidhara et al, 1992) and pea (Smith, 1988;Spano and Timko, 1991) are plastid localized, their primary sequences are no more similar to one another than to that of E. coli PBG deaminase. This suggests that relatively strong selective pressure must exist on the three-dimensional struc- …”

“…A11 PBG deaminases characterized thus far are acidic proteins with monomeric molecular masses between 34 and 44 kD and have optimal pH between 8.0 and 8.5. In animal cells and yeast PBG deaminase is a soluble cytosolic protein (Elder, 1976;Labbe-Bois and Labbe, 1990), whereas in higher plants and algae it is found in the chloroplast stroma (Smith, 1988;Shashidhara and Smith, 1991;Spano and Timko, 1991). Cloned cDNAs and nuclear genes encoding PBG deaminase have now been analyzed from severa1 mammalian cells (e.g.…”

A soluble protein is imported into Euglena chloroplasts as a membrane-bound precursor.

“…A soluble Euglena chloroplast protein, pPBG, was not detected in the Golgi apparatus by immunoelectron microscopy (Shashidhara and Smith, 1991). The pPBG was imported directly into isolated Euglena chloroplasts, and the presequence was removed by a chloroplast-processing peptidase (Shashidhara et al, 1992), suggesting that some precursors are imported from the cytoplasm directly into the chloroplast.…”

“…lmmunoelectron microscopy did not detect the soluble Euglena chloroplast proteins porphobilinogen deaminase (PBG) (Shashidhara and Smith, 1991) and the small subunit of ribulose-l,5-bisphosphate carboxylase/oxygenase (SSU) in the Golgi apparatus. pPBG was imported directly into isolated Euglena chloroplasts and the presequence was cleaved (Shashidhara et al, 1992), suggesting that pPBG is not transported to the Golgi apparatus before chloroplast localization.…”

The Apicoplast: A Review of the Derived Plastid of Apicomplexan Parasites

“…From ALA to tetrapyrroles the pathways are equivalent for both plants and animals and require a further seven enzymes. Curiously, in euglenoids there may only be a plastid set of these downstream enzymes (Shashidhara and Smith, 1991), suggesting that mitochondrial derived ALA may be imported to plastids for further processing.…”