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A novel homodimeric geranyl diphosphate synthase from the orchid Phalaenopsis bellina lacking a DD(X)2-4D motif.
- Source :
-
The Plant journal : for cell and molecular biology [Plant J] 2008 Sep; Vol. 55 (5), pp. 719-33. Date of Electronic Publication: 2008 May 09. - Publication Year :
- 2008
-
Abstract
- Summary: Geranyl diphosphate (GDP) is the precursor of monoterpenes, which are the major floral scent compounds in Phalaenopsis bellina. The cDNA of P. bellina GDP synthase (PbGDPS) was cloned, and its sequence corresponds to the second Asp-rich motif (SARM), but not to any aspartate-rich (Asp-rich) motif. The recombinant PbGDPS enzyme exhibits dual prenyltransferase activity, producing both GDP and farnesyl diphosphate (FDP), and a yeast two-hybrid assay and gel filtration revealed that PbGDPS was able to form a homodimer. Spatial and temporal expression analyses showed that the expression of PbGDPS was flower specific, and that maximal PbGDPS expression was concomitant with maximal emission of monoterpenes on day 5 post-anthesis. Homology modelling of PbGDPS indicated that the Glu-rich motif might provide a binding site for Mg(2+) and catalyze the formation of prenyl products in a similar way to SARM. Replacement of the key Glu residues with alanine totally abolished enzyme activity, whereas their mutation to Asp resulted in a mutant with two-thirds of the activity of the wild-type protein. Phylogenetic analysis indicated that plant GDPS proteins formed four clades: members of both GDPS-a and GDPS-b clades contain Asp-rich motifs, and function as homodimers. In contrast, proteins in the GDPS-c and GDPS-d clades do not contain Asp-rich motifs, but although members of the GDPS-c clade function as heterodimers, PbGDPS, which is more closely related to the GDPS-c clade proteins than to GDPS-a and GDPS-b proteins, and is currently the sole member of the GDPS-d clade, functions as a homodimer.
- Subjects :
- Amino Acid Sequence
Cloning, Molecular
DNA, Complementary genetics
DNA, Plant genetics
Flowers enzymology
Flowers genetics
Gene Expression
Genes, Plant
Models, Molecular
Molecular Sequence Data
Monoterpenes metabolism
Mutagenesis, Site-Directed
Odorants
Phylogeny
Plant Proteins metabolism
RNA, Plant genetics
Recombinant Proteins genetics
Recombinant Proteins metabolism
Reverse Transcriptase Polymerase Chain Reaction
Sequence Alignment
Sequence Homology, Amino Acid
Dimethylallyltranstransferase genetics
Orchidaceae enzymology
Orchidaceae genetics
Plant Proteins genetics
Subjects
Details
- Language :
- English
- ISSN :
- 1365-313X
- Volume :
- 55
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- The Plant journal : for cell and molecular biology
- Publication Type :
- Academic Journal
- Accession number :
- 18466308
- Full Text :
- https://doi.org/10.1111/j.1365-313X.2008.03547.x