Type III secretion of the Salmonella effector protein SopE is mediated via an N-terminal amino acid signal and not an mRNA sequence.
Type III secretion systems (TTSS) are virulence-associated components of many gram-negative bacteria that translocate bacterial proteins directly from the bacterial cytoplasm into the host cell. The Salmonella translocated effector protein SopE has no consensus cleavable amino-terminal secretion sequence, and the mechanism leading to its secretion through the Salmonella pathogenicity island 1 (SPI-1) TTSS is still not fully understood. There is evidence from other bacteria which suggests that the TTSS signal may reside within the 5' untranslated region (UTR) of the mRNA of secreted effectors. We investigated the role of the 5' UTR in the SPI-1 TTSS-mediated secretion of SopE using promoter fusions and obtained data indicating that the mRNA sequence is not involved in the secretion process. To clarify the proteinaceous versus RNA nature of the signal, we constructed frameshift mutations in the amino-terminal region of SopE of Salmonella enterica serovar Typhimurium SL1344. Only constructs with the native amino acid sequence were secreted, highlighting the importance of the amino acid sequence versus the mRNA sequence for secretion. Additionally, we obtained frameshift mutation data suggesting that the first 15 amino acids are important for secretion of SopE independent of the presence of the chaperone binding site. These data shed light on the nature of the signal for SopE secretion and highlight the importance of the amino-terminal amino acids for correct targeting and secretion of SopE via the SPI-1-encoded TTSS during host cell invasion.
Karavolos
M H
MH
Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle upon Tyne, NE2 4HH, United Kingdom.
Roe
A J
AJ
Wilson
M
M
Henderson
J
J
Lee
J J
JJ
Gally
D L
DL
Khan
C M A
CM
D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016368:Frameshift Mutation; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D021381:Protein Transport; D012333:RNA, Messenger / Q000737:chemistry / Q000502:physiology; D012486:Salmonella typhimurium / Q000502:physiology*
D001426:Bacterial Proteins; D012333:RNA, Messenger; C103987:SopE protein, Salmonella
Mol Microbiol. 1999 Nov;34(4):850-64
10564523
Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):2574-9
9482928
Infect Immun. 1999 Dec;67(12):6385-93
10569754
Mol Microbiol. 2000 Jun;36(5):997-1005
10844685
Mol Microbiol. 2000 Jun;36(5):1015-23
10844687
Proc Natl Acad Sci U S A. 2000 Jun 20;97(13):7539-44
10861017
Infect Immun. 2000 Sep;68(9):5050-5
10948124
Proc Natl Acad Sci U S A. 2000 Aug 29;97(18):10225-30
10944190
Nucleic Acids Res. 2001 Jan 1;29(1):148-51
11125074
Mol Microbiol. 2001 Jan;39(2):248-59
11136447
Nature. 2001 Oct 25;413(6858):852-6
11677609
J Bacteriol. 2002 Mar;184(5):1287-95
11844757
J Exp Med. 2002 May 6;195(9):1155-66
11994420
J Bacteriol. 2002 Jun;184(12):3321-8
12029049
Annu Rev Cell Dev Biol. 2002;18:107-33
12142275
J Bacteriol. 2002 Nov;184(21):5880-93
12374821
Infect Immun. 2003 Oct;71(10):5900-9
14500511
J Bacteriol. 2003 Dec;185(23):6950-67
14617659
Mol Microbiol. 2003 Nov;50(4):1189-98
14622408
J Bacteriol. 2003 Dec;185(24):7279-84
14645290
J Bacteriol. 2004 Feb;186(3):829-41
14729710
J Bacteriol. 2004 Feb;186(4):1215-9
14762020
J Bacteriol. 1978 Jun;134(3):1141-56
149110
Cold Spring Harb Symp Quant Biol. 1979;43 Pt 1:77-90
383387
Nature. 1981 May 21;291(5812):238-9
7015147
J Bacteriol. 1995 Jul;177(14):4121-30
7608087
Proc Natl Acad Sci U S A. 1995 Dec 19;92(26):11998-2002
8618831
Mol Microbiol. 1996 Apr;20(2):255-62
8733225
EMBO J. 1996 Oct 1;15(19):5191-201
8895564
Mol Microbiol. 1996 Oct;22(2):327-38
8930917
J Bacteriol. 1996 Dec;178(24):7227-33
8955406
Science. 1997 Nov 7;278(5340):1140-3
9353199
Infect Immun. 1998 Apr;66(4):1432-8
9529064
J Bacteriol. 1998 Apr;180(7):1793-802
9537377
Science. 1998 Apr 24;280(5363):602-5
9554854
Microbiol Mol Biol Rev. 1998 Jun;62(2):379-433
9618447
Cell. 1998 May 29;93(5):815-26
9630225
Mol Microbiol. 1998 Oct;30(1):163-74
9786193
Mol Microbiol. 1999 Feb;31(3):971-82
10048039
Curr Opin Microbiol. 1999 Feb;2(1):18-24
10047552
Curr Opin Microbiol. 1999 Feb;2(1):46-50
10047557
Mol Microbiol. 1999 Feb;31(4):1139-48
10096081
Infect Immun. 1999 Aug;67(8):4099-105
10417179
Infect Immun. 1999 Sep;67(9):4879-85
10456944