Abstract: A recombinant DNA cloning vector useful for expressing exogenous protein is described, which comprises(a) a DNA segment containing a functional origin of replication;(b) one or more DNA segments, each of which conveys to a transformable host cell a property useful for selection when said vector is transformed into said host cell; and(c) a DNA segment comprising a sequence that defines, in tandem,(1) the promoter of a lipoprotein expression control sequence,(2) the 5' untranslated region of a lipoprotein expression control sequence and(3) a translation start codon followed, without interposition of a portion or all of a nucleotide sequence coding for endogenous protein, by a nucleotide sequence coding for an enterokinase cleavage site to which is joined, without interruption, a nucleotide sequence coding for an exogenous protein.