Structural analysis and molecular model of a self-incompatibility RNase from wild tomato.
Self-incompatibility RNases (S-RNases) are an allelic series of style glycoproteins associated with rejection of self-pollen in solanaceous plants. The nucleotide sequences of S-RNase alleles from several genera have been determined, but the structure of the gene products has only been described for those from Nicotiana alata. We report on the N-glycan structures and the disulfide bonding of the S3-RNase from wild tomato (Lycopersicon peruvianum) and use this and other information to construct a model of this molecule. The S3-RNase has a single N-glycosylation site (Asn-28) to which one of three N-glycans is attached. S3-RNase has seven Cys residues; six are involved in disulfide linkages (Cys-16-Cys-21, Cys-46-Cys-91, and Cys-166-Cys-177), and one has a free thiol group (Cys-150). The disulfide-bonding pattern is consistent with that observed in RNase Rh, a related RNase for which radiographic-crystallographic information is available. A molecular model of the S3-RNase shows that four of the most variable regions of the S-RNases are clustered on one surface of the molecule. This is discussed in the context of recent experiments that set out to determine the regions of the S-RNase important for recognition during the self-incompatibility response.
Parry
S
S
Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville, VIC, Australia.
Newbigin
E
E
Craik
D
D
Nakamura
K T
KT
Bacic
A
A
Oxley
D
D
D000595:Amino Acid Sequence; D002240:Carbohydrate Sequence; D004220:Disulfides / Q000737:chemistry; D018551:Solanum lycopersicum / Q000201:enzymology*; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry; D011487:Protein Conformation; D012260:Ribonucleases / Q000737:chemistry* / Q000235:genetics
D004220:Disulfides; D011134:Polysaccharides; D012260:Ribonucleases; C110993:self-incompatibility ribonuclease S3