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Plasmid F replication is controlled by a plasmid-specified Rep protein with both autorepressor and initiator functions. The mechanism by which these two functions of a Rep protein are balanced to achieve stable replication is unknown; however, we speculated in prior work that Rep protein modification could be involved. We report here that naturally proteolyzed F RepE protein has been detected and characterized. The processed molecule lost the first 17 N-terminal aminoacyl residues and initiator function but acquired increased specific DNA-binding affinity in the presence of Escherichia coli chromosomal DNA. When supplied in trans, the altered protein acts as an incompatibility substance and eliminates maintenance of F'lac. These findings indicate that protein processing has the potential to contribute to the overall control of DNA replication.

PNMT (EC 2.1.1.28) catalyzes the N-methylation of norepinephrine to form epinephrine. We set out to resequence the human PNMT gene, including all exons and introns as well as approximately 1 kb of the 5`-flanking region using Coriell Institute DNA samples from 60 African-American (AA) and 60 Caucasian-American (CA) subjects. Within the 3.5 kb resequenced, 17 single nucleotide polymorphisms (SNPs) were observed, including 3 nonsynonymous cSNPs (Asn9Ser, Thr98Ala and Arg112Cys). When constructs for the nonsynonymous cSNPs were transiently expressed in COS-1 cells, the Ala98 allozyme displayed virtually no enzyme activity or immunoreactive protein when compared with the wild type (WT) allozyme (P<0.01), while values for the other variant allozymes did not differ significantly from those for WT. Rabbit reticulocyte lysate studies showed that the decrease in immunoreactive protein for the Ala98 allozyme was due–at least in part–to accelerated protein degradation. These observations raise the possibility of inherited variation in the ability to form epinephrine from norepinephrine.Clinical Pharmacology & Therapeutics (2004) 75, P95–P95; doi: 10.1016/j.clpt.2003.11.361