However, it has previously been shown that NEP/CD10 is constitutively expressed by alveolar and airway epithelial cells in vivo. This indicates that the PPT-A precursor observed in airway epithelia will be processed into active peptides and be able to exert their effects locally. Expression of LacZ in airway epithelial cells was initiated at a very early time after infection and persisted, through 7 days. This is unusual as the induction of most proinflammatory and immunomodulatory mediators in the lungs of mice in viral respiratory challenge models does not occur until at least 3 days, peaking around 6 through 10 days p.i.. Synchronized cultures have been used to detect cell-cycle dependent localization of several structural and signaling proteins, but the number of proteins whose localization changes through the cell cycle is not known. To identify clones with localized fluorescence, cells from each colony were grown to exponential phase in liquid medium and observed using epifluorescence microscopy. The majority of the clones produced an even distribution of cytoplasmic fluorescence, similar to C. crescentus producing GFP with no fusion. However, over 1,000 clones with localized GFP fluorescence were recovered. Twenty-four clones with representative localization patterns were chosen for further investigation, and the transposon insertion site was determined by either arbitrary PCR or inverse PCR, followed by DNA sequencing. The identity of each GFP fusion protein was determined by conceptual translation of the DNA sequence. Of the sequenced clones, seven independent insertions were recovered in each of two genes, rsaA and serA and one insertion was recovered in each of ten different genes. The transposon screen identified five proteins predicted to be localized based on similarity to proteins from other species, or on bioinformatic algorithms. CheR, a protein methyl Sibutramine HCl transferase component of the Resibufogenin chemosensory system, was found in a single focus at either the pole or mid-cell. Although CheR has not been studied in C. crescentus, it is localized in a focus near the cell pole in other bacteria, and other chemosensory proteins are localized to the flagellar pole in C. crescentus. The transposon insertion in cheR resulted in fusion of the first 267 residues of the 293 residue protein to GFP.