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.