Nucleotide sequences of two minireplicon fragments of the p1414 cryptic plasmid of Bacillus subtilis were determined. The fragments corresponded to the region containing ori(+) and the gene coding for Rep protein. Comparing sequences of the fragments with corresponding sequences of other ss+ plasmids suggested that ori(+) of p1414 belongs to the family of endogenous cryptic B. subtilis plasmids, which form an individual, closely related subgroup in the group of ori(+) sequences of the pC194 type. It was found that the amino acid sequence of a conservative FLTLTV motif located, together with its flanking sequences, at the N ends of Rep proteins encoded by different ss+ plasmids, is similar to those of several transmembrane proteins and signal peptides. These results, together with computer data on predicting the secondary and tertiary structure of the N-terminal domain of the p1414 Rep protein, suggest that the domain can serve as a "membrane anchor" during plasmid replication.