Five genes at the 3' end of the Klebsiella pneumoniae pulC operon are required for pullulanase secretion

The nucleotide sequence of a 5082bp fragment of chromosomal DNA from Klebsiella pneumoniae strain UNF5023 is reported. The sequence includes the last four genes of an operon of genes specifically required for the secretion of the enzyme pullulanase. All four genes (puIL, puIM, puIN and puIO) are shown to be required for pullulanase secretion, as is a fifth gene (puIK) which extends beyond the 5′ end of the sequenced DNA. The products of the puIL, puIM, puIN and puIO genes (44kD, 18kD, 27kD and 24kD, respectively) are all predicted to have one or more hydrophobic domains typical of signal sequences and/or membrane anchors, and were all found mainly associated with the inner membranes of subfractionated cells in which the corresponding genes had been expressed from the bacteriophage T7 gene 10 promoter. The results of this study increase the number of genes which have been identified as required for pullulanase secretion to eight, in addition to genes coding for components of the general export pathway.