Table 5. Cnr interference with α–α interaction.

	Plasmida		Protein expressed from the plasmidb		Efficiency of platingc
	Low copy number	High copy number	Low concentration	High concentration	λ	λcY17	λ668
A	pGM776	–	CI∼α620–777	–	<10–5	<10–5	1
	pGM738	–	CI∼α664–777	–	<10–5	<10–5	1
	pGM740	–	CI∼α741–777	–	1	1	1
	pC168	–	CI∼Rop	–	<10–5	<10–5	1
B	pGM776	pGM727	CI∼α620–777	CI*∼Cnr	1	1	1
	pGM776	pC169	CI∼α620–777	CI*∼Rop	<10–5	<10–5	1
	pGM738	pGM727	CI∼α664–777	CI*∼Cnr	1	1	1
	pGM738	pC169	CI∼α664–777	CI*∼Rop	<10–5	<10–5	1
	pGM740	pGM727	CI∼α741–777	CI*∼Cnr	1	1	1
	pGM740	pC169	CI∼α741–777	CI*∼Rop	1	1	1
	pC168	pGM727	CI∼Rop	CI*∼Cnr	< 10–5	< 10–5	1
	pC168	pC169	CI∼Rop	CI*∼Rop	1	1	1
C	pGM778	pGM727	CI∼αcr620–777G732W	CI*∼Cnr	1	1	1
	pGM778	pC169	CI∼αcr620–777G732W	CI*∼Rop	<10–5	<10–5	1
	pGM779	pGM727	CI∼αcr620–777G732V	CI*∼Cnr	1	1	1
	pGM779	pC169	CI∼αcr620–777G732V	CI*∼Rop	<10–5	<10–5	1
	pGM780	pGM727	CI∼αcr620–777T675M	CI*∼Cnr	1	1	1
	pGM780	pC169	CI∼αcr620–777T675M	CI*∼Rop	<10–5	<10–5	1
D	pGM776	pGM283	CI∼α620–777	Cnr	1	1	1
	pGM779	pGM283	CI∼αcr620–777G732V	Cnr	1	1	1
	pGM776	pST106d	CI∼α620–777	Cnrd	0.25	0.25	1
	pGM779	pST106d	CI∼αcr620–777G732V	Cnrd	0.25	0.25	1
	pGM794	pGM722	CI*∼Cnr	CI∼α620–777	<10–5	<10–5	1
	pGM794	pGM774	CI*∼Cnr	CI∼αcr620–777G732V	<10–5	<10–5	1

^aThe plasmids are carried by strain CSH50. Low copy number plasmids are derivatives of pC168 (p15A origin); high copy number plasmids are derivatives of pC169, pC132 or pUC19 (ColE1 origin).

^bThe P4 protein fused to the N-terminal region of either the wild-type λ repressor (CI) or the mutant repressor (CI*) are indicated. The α protein residues and the α^cr amino acids substitutions are reported.

^cEfficiency of plating was measured as indicated in Materials and Methods. λ, wild-type; λcY17, immunity sensitive; λ668, virulent mutant.

^dLow copy number plasmid (derivative of pMS119EH; oriV) and low concentration of the protein expressed.