Transcriptional regulation of the S-layer protein type I secretion system in Caulobacter crescentus

Toporowski, Michael C. ; Nomellini, John F. ; Awram, Peter ; Levi, Assaf ; Smit, John

In: FEMS Microbiology Letters, 2005, vol. 251, no. 1, p. 29-36

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    Summary
    The Gram-negative Caulobacter crescentus exports RsaA, the crystalline S-layer subunit protein using a dedicated type I secretion system. The protein and two transporter genes (rsaADE) are located together, comparable to the Escherichia coli type I hemolysin hlyCABD operon, where read through of a stem loop following hlyCA results in reduced transcription of the hlyBD. Using two genetic approaches and a direct assessment of transcription from regions 5′ to the genes we learned that rsaD and rsaE were transcribed together as a separate transcript from rsaA. These results are contrary to previous assumptions about the rsaADE type I secretion gene control and add another theme to the area of type I secretion transcription regulation. It may be that to accommodate the high levels of RsaA secretion, the type I transporters must be transcribed independently from rsaA