1etl: Difference between revisions

Revision as of 13:31, 21 February 2008

STRUCTURAL CHARACTERISTICS FOR BIOLOGICAL ACTIVITY OF HEAT-STABLE ENTEROTOXIN PRODUCED BY ENTEROTOXIGENIC ESCHERICHIA COLI: X-RAY CRYSTALLOGRAPHY OF WEAKLY TOXIC AND NONTOXIC ANALOGS

OverviewOverview

Heat-stable enterotoxin (ST) produced by a pathogenic strain of Escherichia coli exerts its function by binding to a membrane-bound guanylyl cyclase on intestinal epithelial cell membranes, which in turn catalyzes the production of cyclic GMP as a second messenger in the cells. To elucidate the structural requirements for the biological activities of ST, we synthesized [Mpr5,Gly13]STp(5-17) and [Mpr5,Leu13]STp(5-17), which are weakly toxic and nontoxic analogs of STp, in which the toxic domain consists of the sequence from Cys at position 5 to Cys at position 17. In these analogs, Cys at position 5 is replaced by Mpr (beta-mercaptopropionic acid) and Ala at position 13 by Gly and Leu, respectively. We examined these analogs by X-ray diffraction analysis using direct methods and refined the structures to crystallographic R factors of 7.3% and 6.6% using 5492 and 5122 data, respectively, observed > 3 sigma (Fo) with a resolution of 0.89 A. These peptides have a right-handed spiral structure consisting of three structural segments: an N-terminal 3(10) helix, a central type I beta-turn, and a C-terminal type II beta-turn. These structures show minor differences from that of [Mpr5]STp(5-17), the fully toxic analog of heat-stable enterotoxin [Ozaki et al. (1991) J. Biol. Chem. 266, 5934-5941], suggesting that the decrease and loss of the biological activities of [Mpr5,Gly13]STp(5-17) and [Mpr5,Leu13]STp(5-17), respectively, are not caused by structural changes but are associated with the direct interaction of Ala13 with the receptor protein. Careful comparison of these structures in crystalline states revealed that ST has the following structural characteristics: (i) inherent flexibility at the junctions of the three segments and in the central segment, which includes the putative receptor-binding residues, Ala13, (ii) a specific hydrophobic character around the central segment, and (iii) an unexpected C-terminal folding similar to those of functionally unrelated peptides that are known to be ionophores.

About this StructureAbout this Structure

1ETL is a Single protein structure of sequence from [1]. Full crystallographic information is available from OCA.

ReferenceReference

Structural characteristics for biological activity of heat-stable enterotoxin produced by enterotoxigenic Escherichia coli: X-ray crystallography of weakly toxic and nontoxic analogs., Sato T, Ozaki H, Hata Y, Kitagawa Y, Katsube Y, Shimonishi Y, Biochemistry. 1994 Jul 26;33(29):8641-50. PMID:8038153 [[Category: ]]

Page seeded by OCA on Thu Feb 21 12:31:21 2008

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

OCA

@@ Line 1: / Line 1: @@
-[[Image:1etl.gif|left|200px]]<br /><applet load="1etl" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1etl.gif|left|200px]]<br /><applet load="1etl" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1etl, resolution 0.89&Aring;" />
 '''STRUCTURAL CHARACTERISTICS FOR BIOLOGICAL ACTIVITY OF HEAT-STABLE ENTEROTOXIN PRODUCED BY ENTEROTOXIGENIC ESCHERICHIA COLI: X-RAY CRYSTALLOGRAPHY OF WEAKLY TOXIC AND NONTOXIC ANALOGS'''<br />
 ==Overview==
-Heat-stable enterotoxin (ST) produced by a pathogenic strain of, Escherichia coli exerts its function by binding to a membrane-bound, guanylyl cyclase on intestinal epithelial cell membranes, which in turn, catalyzes the production of cyclic GMP as a second messenger in the cells., To elucidate the structural requirements for the biological activities of, ST, we synthesized [Mpr5,Gly13]STp(5-17) and [Mpr5,Leu13]STp(5-17), which, are weakly toxic and nontoxic analogs of STp, in which the toxic domain, consists of the sequence from Cys at position 5 to Cys at position 17. In, these analogs, Cys at position 5 is replaced by Mpr, (beta-mercaptopropionic acid) and Ala at position 13 by Gly and Leu, respectively. We examined these analogs by X-ray diffraction analysis, using direct methods and refined the structures to crystallographic R, factors of 7.3% and 6.6% using 5492 and 5122 data, respectively, observed, &gt; 3 sigma (Fo) with a resolution of 0.89 A. These peptides have a, right-handed spiral structure consisting of three structural segments: an, N-terminal 3(10) helix, a central type I beta-turn, and a C-terminal type, II beta-turn. These structures show minor differences from that of, [Mpr5]STp(5-17), the fully toxic analog of heat-stable enterotoxin [Ozaki, et al. (1991) J. Biol. Chem. 266, 5934-5941], suggesting that the decrease, and loss of the biological activities of [Mpr5,Gly13]STp(5-17) and, [Mpr5,Leu13]STp(5-17), respectively, are not caused by structural changes, but are associated with the direct interaction of Ala13 with the receptor, protein. Careful comparison of these structures in crystalline states, revealed that ST has the following structural characteristics: (i), inherent flexibility at the junctions of the three segments and in the, central segment, which includes the putative receptor-binding residues, Ala13, (ii) a specific hydrophobic character around the central segment, and (iii) an unexpected C-terminal folding similar to those of, functionally unrelated peptides that are known to be ionophores.
+Heat-stable enterotoxin (ST) produced by a pathogenic strain of Escherichia coli exerts its function by binding to a membrane-bound guanylyl cyclase on intestinal epithelial cell membranes, which in turn catalyzes the production of cyclic GMP as a second messenger in the cells. To elucidate the structural requirements for the biological activities of ST, we synthesized [Mpr5,Gly13]STp(5-17) and [Mpr5,Leu13]STp(5-17), which are weakly toxic and nontoxic analogs of STp, in which the toxic domain consists of the sequence from Cys at position 5 to Cys at position 17. In these analogs, Cys at position 5 is replaced by Mpr (beta-mercaptopropionic acid) and Ala at position 13 by Gly and Leu, respectively. We examined these analogs by X-ray diffraction analysis using direct methods and refined the structures to crystallographic R factors of 7.3% and 6.6% using 5492 and 5122 data, respectively, observed &gt; 3 sigma (Fo) with a resolution of 0.89 A. These peptides have a right-handed spiral structure consisting of three structural segments: an N-terminal 3(10) helix, a central type I beta-turn, and a C-terminal type II beta-turn. These structures show minor differences from that of [Mpr5]STp(5-17), the fully toxic analog of heat-stable enterotoxin [Ozaki et al. (1991) J. Biol. Chem. 266, 5934-5941], suggesting that the decrease and loss of the biological activities of [Mpr5,Gly13]STp(5-17) and [Mpr5,Leu13]STp(5-17), respectively, are not caused by structural changes but are associated with the direct interaction of Ala13 with the receptor protein. Careful comparison of these structures in crystalline states revealed that ST has the following structural characteristics: (i) inherent flexibility at the junctions of the three segments and in the central segment, which includes the putative receptor-binding residues, Ala13, (ii) a specific hydrophobic character around the central segment, and (iii) an unexpected C-terminal folding similar to those of functionally unrelated peptides that are known to be ionophores.
 ==About this Structure==
-ETL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/ ]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ETL OCA].
+ETL is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/ ]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ETL OCA].
 ==Reference==
@@ Line 17: / Line 17: @@
 [[Category: enterotoxin]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 14:18:11 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:31:21 2008''