Regulated expression cloning vectors HELP

[Edgar Valencia]

Hello:
Does anybody know about a regulated expression cloning vector with the 
following characteristics?
a) wide host range
b)incompatibility group other than incP
I've been trying with some derivatives of pMMB (Morales et al Gene 97 
(1991) 39-47) but my problem with this plasmids is that they have the tac 
promoter and the basal expression of my protein is very high even without 
inducer (IPTG), so I can't control my system.

I wish to know too if there are some terminators that could help me to 
reduce the strength of the promoter and the references to get them
with the same pourpose I cloned another another gene between tac and my 
gene to create a "pseudo-operon" but it didn't work. I'm thinking to try 
with other genes among the candidate genes are
Bla
luxab
but I don't know anything about the strength of their terminators so I 
really appreciate any information about it or about other genes I 
can use.

Thanks in advance   

		Edgar Valencia Morales
		CIFN-UNAM
		Departamento de Genetica Molecular
		e-mail edgar at cifn.unam.mx