Identification and characterization of a new lipoprotein, NlpI, in Escherichia coli K-12

We report here the identification of a new lipoprotein, NlpI in Escherichia coli K-12. The NlpI structural gene (nlpI) is located between the genes pn p (polynucleotide phosphorylase) and deaD (RNA helicase) at 71 min on the E . coli chromosome. The nlpI gene encodes a putative polypeptide of approxim ately 34 kDa, and multiple lines of evidence clearly demonstrate that NlpI is indeed a lipoprotein, An nlpI::cm mutation rendered growth of the cells osmotically sensitive, and incubation of the insertion mutant at an elevate d temperature resulted in the formation of filaments. The altered phenotype of the mutant was a direct consequence of the mutation in nlpI, since it w as complemented by the wild-type nlpI gene alone. Overexpression of the una ltered nlpI gene in nlpI gene cells resulted in the loss of the rod morphol ogy and the formation of single prolate ellipsoids and pairs of prolate ell ipsoids joined by partial constrictions. NlpI may be important for an as-ye t undefined step in the overall process of cell division.