Several agrobacteria cause neoplastic diseases in plants, including crown gall disease (Agrobacterium tumefaciens) and hairy root disease (Agrobacterium rhizogenes). The mechanism involves transfer via infective plasmids and subsequent expression of both oncogenes and genes for the synthesis of opines, which can be specifically used as nutrients by the invading bacteria []. Opines are low molecular weight amino acid and sugar phosphate derivatives, e.g., octopine, agropine, and mannopine. The proteins in this group are products of the mas1genes (and homologues) encoding the reductase that produces mannopine from deoxyfructosylglutamine. Subsequently, mannopine can be lactonized to form agropine. The C-terminal short chain dehydrogenase domain is coupled with an N-terminal phosphoglycerate mutase family domain (), the role of which is unknown []. Sequences reported from Ti plasmid pTiC58 are missing half [, ]or all of the N-terminal domain.
Mitochondrial-processing peptidase complex removes the first transit peptide from the N terminus of proteins synthesised in the cytoplasm but destined for the mitochondrion []. The complex is a heterodimer of an alpha and a beta subunit. This entry includes the beta subunit (MAS1 or MPPB; ; MEROPS identifier M16.003), which is a zinc-dependent metallo-endopeptidase that binds one zinc ion via the histidines in an HXXEH motif and a Glu C-terminal to this motif []. MAS1 is itself synthesised in the cytoplasm and has an N-terminal transit peptide [].
The mas proto-oncogene was intially discovered following co-transfection with DNA isolated from a human epidermal carcinoma. It efficiently induces tumorigenicity and has weak focus-inducing activity in NIH 3T3 cells. To date, it is the only oncogene to have been sequenced that encodes a 7TM protein. The oncogene is a GPCR which binds the angiotensin-II metabolite angiotensin (1-7) [, ]. It is therefore thought that MAS1 receptor agonists have similar therapeutic effects as angiotensin-II receptor antagonists including lowering blood pressure []. In the CNS, high levels of the mas proto-oncogene transcript are present in the cerebral cortex, with lower amounts in the hippocampus and cerebellum. In the periphery, it is expressed in low levels in the kidney, adrenals and liver. The rat RTA protein has some similarity to the mas proto-oncogene sequence.
