PMID:14617068

Citation	Williams, PM and Barkan, A (2003) A chloroplast-localized PPR protein required for plastid ribosome accumulation. Plant J. 36:675-86
Abstract	The pentatricopeptide repeat (PPR) is a degenerate 35-amino acid repeating motif that is found in animal, fungal, and plant proteins. The PPR protein family is particularly large in plants, where the majority of family members are predicted to be targeted to mitochondria or chloroplasts. PPR proteins are believed to fall into the larger family of helical repeat proteins, which typically bind macromolecules through a surface formed by the stacking of consecutive helical repeating units. Prior findings implicate several PPR proteins in organellar RNA metabolism, but the biological functions of few PPR proteins have been explored and in no case has a direct substrate been definitively identified. We present a characterization of the maize nuclear gene ppr2, which encodes a chloroplast PPR protein. PPR2 is found in large, heterogeneous protein complexes in the chloroplast stroma, some of which may be associated with RNA. Null ppr2 mutants have albino leaves and lack plastid rRNA and translation products. Plastid rRNAs are absent in both dark- and light-grown leaf tissues, indicating that their absence does not result from photo-oxidative damage. The population of plastid transcripts in ppr2 mutants is similar to that in other maize mutants lacking plastid ribosomes, and no ppr2-specific defects in plastid RNA metabolism have been detected. Taken together, the results suggest that ppr2 functions in the synthesis or assembly of one or more component of the plastid translation machinery.
Links	PubMed
Keywords	Amino Acid Sequence; Base Sequence; Chloroplasts/metabolism; Cloning, Molecular; Conserved Sequence; DNA Primers; Models, Molecular; Molecular Sequence Data; Plant Proteins/chemistry; Plant Proteins/genetics; Plant Proteins/metabolism; Plastids/genetics; Polymerase Chain Reaction; Protein Conformation; Ribosomes/genetics; Sequence Alignment; Sequence Homology, Amino Acid; Zea mays/genetics; Zea mays/metabolism
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
MAIZE:Q7Y1W6		GO:0009570: chloroplast stroma	ECO:0000314:		C		Figure 3c: When isolated chloroplasts were fractionated, PPR2 co-fractionated with Cpn60, a stromal marker, and did not co-fractionate with proteins associated with the stromal face of the thylakoid membrane (ATPβ), the thylakoid lumen (OE33), or the envelope membranes (IM35). Therefore, PPR2 is localized to the chloroplast stroma.	complete
MAIZE:Q7Y1W6		GO:0043473: pigmentation	ECO:0000314:		P		Figure 5c: Homozygous ppr2-1 and ppr2-4 mutant seedlings are albino, with an ‘ivory’ leaf phenotype. Crosses between ppr2-1/+ and ppr2-4/+ plants yielded approximately 25% albino seedlings, indicating that the ivory leaf phenotype results from the mutations in ppr2.	complete
MAIZE:ATPB		GO:0042651: thylakoid membrane	ECO:0000314:		C		Figure 3c: immunoblot analysis of chloroplast sub-fractions shows that ATPB resides in the thylakoid lumen	complete

References

See Help:References for how to manage references in GONUTS.