TABLE 1.

C-terminal sequences of Mob proteins from different pBBR1 derivatives and their corresponding mobilization frequencies^a

Plasmid (selective marker)b	C-terminal sequencec	Mobilization frequencyd
	322    329
	↓     ↓
pBBR1 (none)	.ERGRDRGGYSR	ND
pBBR1CM (KAN, CHL)	.ERGRAHFPEKCHLTSKKPLLS	8 × 10−2
pBBR1MCS-2 (KAN)	.ERGRAHFPEKCHLG	1 × 10−1
pBBR1MCS-4 (AMP)	.ERGRAHFPEKCHLDFGHEILKKDLHLDPFKLKMKF	8 × 10−2
pBBR1MCS-5 (GEN)	.ERGRAHFPEKCHLAAL	3 × 10−2
pBBR122 (KAN, CHL)	Frameshift mutation	7 × 10−7
pBBR122 (complementation by pMOB3)		1 × 10−2
pBHR1 (KAN, CHL)	.ERGRAHFPEKCHLTSKKPLLS	1 × 10−1

^aFor the mobilization experiments, Nal^s S17-1 bacteria (45) containing one of the plasmids to be tested were used as donors and the Nal^r F⁻ strain XA106 (from our laboratory collection) was used as a recipient. Matings were performed at 30°C on LB plates as described previously (26). After overnight incubation, the transconjugants were selected at 30°C on LB plates supplemented with nalidixic acid (20 μg/ml) and the antibiotic allowing selection of the bacteria with the mobilizable plasmid (kanamycin at 50 μg/ml, ampicillin at 100 μg/ml, gentamicin at 10 μg/ml, or chloramphenicol at 15 μg/ml). 

^bKAN, kanamycin; CHL, chloramphenicol; AMP, ampicillin; GEN, gentamicin. Plasmid pMOB3 contains a functional mob gene and the 327-bp sequence upstream from this gene (oriT), cloned in the pCRBlunt vector. 

^cThe C-terminal sequence of each Mob protein is represented; the coordinates are positions in the pBBR1CM Mob protein. Amino acids modified in the Mob protein of the pBBR1 derivative are boldfaced. 

^dCalculated as the ratio of the number of transconjugants to the number of recipients. ND, not determined.