The Salmonella type III secretion system inner rod protein PrgJ is partially folded

Dalian Zhong, Matthew Lefebre, Kawaljit Kaur, Melanie A. Mcdowell, Courtney Gdowski, Sunhwan Jo, Yu Wang, Stephen H. Benedict, Susan M. Lea, Jorge E. Galan, Roberto N. De Guzman

Research output: Contribution to journalArticleResearchpeer-review

29 Citations (Scopus)


The type III secretion system (T3SS) is essential in the pathogenesis of many bacteria. The inner rod is important in the assembly of the T3SS needle complex. However, the atomic structure of the inner rod protein is currently unknown. Based on computational methods, others have suggested that the Salmonella inner rod protein PrgJ is highly helical, forming a folded 3 helix structure. Here we show by CD and NMR spectroscopy that the monomeric form of PrgJ lacks a tertiary structure, and the only well-structured part of PrgJ is a short α-helix at the C-terminal region from residues 65-82. Disruption of this helix by glycine or proline mutation resulted in defective assembly of the needle complex, rendering bacteria incapable of secreting effector proteins. Likewise, CD and NMR data for the Shigella inner rod protein MxiI indicate this protein lacks a tertiary structure as well. Our results reveal that the monomeric forms of the T3SS inner rod proteins are partially folded.

Original languageEnglish
Pages (from-to)25303-25311
Number of pages9
JournalJournal of Biological Chemistry
Issue number30
Publication statusPublished - 20 Jul 2012
Externally publishedYes

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