1atd: Difference between revisions

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HIGH-RESOLUTION STRUCTURE OF ASCARIS TRYPSIN INHIBITOR IN SOLUTION: DIRECT EVIDENCE FOR A PH INDUCED CONFORMATIONAL TRANSITION IN THE REACTIVE SITE

OverviewOverview

BACKGROUND: The Ascaris trypsin inhibitor (ATI) is a member of a new family of serine protease inhibitors isolated from the helminthic worm Ascaris lumbricoides var suum. This family comprises five chymotrypsin/elastase inhibitors and one trypsin inhibitor. Members are characterized by the presence of five disulfide bonds (two of which are located on either side of the reactive site) in a single small protein domain of 61-62 residues. RESULTS: The solution structure of ATI has been determined at pH 2.4 and pH 4.75 by NMR spectroscopy. Iterative refinement permitted the unambiguous assignment of the pairing of the five disulfide bridges (Cys5-Cys38, Cys15-Cys33, Cys18-Cys29, Cys22-Cys60, and Cys40-Cys54) which were previously unknown. The structure includes four short beta-strands arranged in two approximately perpendicular beta-sheets. The reactive site loop is bounded by two disulfide bridges (Cys15-Cys33 and Cys18-Cys29) and is part of the long loop (residues 15-25) connecting strands beta 1 and beta 2. Comparison of the nuclear Overhauser enhancement data at the two pH values revealed significant differences centered around the reactive site. While the reactive site at pH 2.4 closely resembles that of other protease inhibitors, at pH 4.75 the reactive site loop undergoes a major conformational rearrangement involving the psi backbone torsion angles of the P2, P1 and P1' residues (residues 30-32). This is associated with a change in the positions of the side chains of Arg31 and Glu32. CONCLUSIONS: The overall three-dimensional structure of ATI posesses an unusual fold and, with the exception of the reactive site, shows no similarity to other serine protease inhibitors. The observation that the reactive site of the low pH form of ATI is similar to that of other serine proteases suggests that this is the active form of the protein.

About this StructureAbout this Structure

1ATD is a Single protein structure of sequence from Ascaris suum. Full crystallographic information is available from OCA.

ReferenceReference

High-resolution structure of Ascaris trypsin inhibitor in solution: direct evidence for a pH-induced conformational transition in the reactive site., Grasberger BL, Clore GM, Gronenborn AM, Structure. 1994 Jul 15;2(7):669-78. PMID:7922043

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 '''HIGH-RESOLUTION STRUCTURE OF ASCARIS TRYPSIN INHIBITOR IN SOLUTION: DIRECT EVIDENCE FOR A PH INDUCED CONFORMATIONAL TRANSITION IN THE REACTIVE SITE'''<br />
 ==Overview==
-BACKGROUND: The Ascaris trypsin inhibitor (ATI) is a member of a new, family of serine protease inhibitors isolated from the helminthic worm, Ascaris lumbricoides var suum. This family comprises five, chymotrypsin/elastase inhibitors and one trypsin inhibitor. Members are, characterized by the presence of five disulfide bonds (two of which are, located on either side of the reactive site) in a single small protein, domain of 61-62 residues. RESULTS: The solution structure of ATI has been, determined at pH 2.4 and pH 4.75 by NMR spectroscopy. Iterative refinement, permitted the unambiguous assignment of the pairing of the five disulfide, bridges (Cys5-Cys38, Cys15-Cys33, Cys18-Cys29, Cys22-Cys60, and, Cys40-Cys54) which were previously unknown. The structure includes four, short beta-strands arranged in two approximately perpendicular, beta-sheets. The reactive site loop is bounded by two disulfide bridges, (Cys15-Cys33 and Cys18-Cys29) and is part of the long loop (residues, 15-25) connecting strands beta 1 and beta 2. Comparison of the nuclear, Overhauser enhancement data at the two pH values revealed significant, differences centered around the reactive site. While the reactive site at, pH 2.4 closely resembles that of other protease inhibitors, at pH 4.75 the, reactive site loop undergoes a major conformational rearrangement, involving the psi backbone torsion angles of the P2, P1 and P1' residues, (residues 30-32). This is associated with a change in the positions of the, side chains of Arg31 and Glu32. CONCLUSIONS: The overall three-dimensional, structure of ATI posesses an unusual fold and, with the exception of the, reactive site, shows no similarity to other serine protease inhibitors., The observation that the reactive site of the low pH form of ATI is, similar to that of other serine proteases suggests that this is the active, form of the protein.
+BACKGROUND: The Ascaris trypsin inhibitor (ATI) is a member of a new family of serine protease inhibitors isolated from the helminthic worm Ascaris lumbricoides var suum. This family comprises five chymotrypsin/elastase inhibitors and one trypsin inhibitor. Members are characterized by the presence of five disulfide bonds (two of which are located on either side of the reactive site) in a single small protein domain of 61-62 residues. RESULTS: The solution structure of ATI has been determined at pH 2.4 and pH 4.75 by NMR spectroscopy. Iterative refinement permitted the unambiguous assignment of the pairing of the five disulfide bridges (Cys5-Cys38, Cys15-Cys33, Cys18-Cys29, Cys22-Cys60, and Cys40-Cys54) which were previously unknown. The structure includes four short beta-strands arranged in two approximately perpendicular beta-sheets. The reactive site loop is bounded by two disulfide bridges (Cys15-Cys33 and Cys18-Cys29) and is part of the long loop (residues 15-25) connecting strands beta 1 and beta 2. Comparison of the nuclear Overhauser enhancement data at the two pH values revealed significant differences centered around the reactive site. While the reactive site at pH 2.4 closely resembles that of other protease inhibitors, at pH 4.75 the reactive site loop undergoes a major conformational rearrangement involving the psi backbone torsion angles of the P2, P1 and P1' residues (residues 30-32). This is associated with a change in the positions of the side chains of Arg31 and Glu32. CONCLUSIONS: The overall three-dimensional structure of ATI posesses an unusual fold and, with the exception of the reactive site, shows no similarity to other serine protease inhibitors. The observation that the reactive site of the low pH form of ATI is similar to that of other serine proteases suggests that this is the active form of the protein.
 ==About this Structure==
-ATD is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ascaris_suum Ascaris suum]. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1ATD OCA].
+ATD is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ascaris_suum Ascaris suum]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ATD OCA].
 ==Reference==
@@ Line 13: / Line 13: @@
 [[Category: Ascaris suum]]
 [[Category: Single protein]]
-[[Category: Clore, G.M.]]
+[[Category: Clore, G M.]]
-[[Category: Grasberger, B.L.]]
+[[Category: Grasberger, B L.]]
-[[Category: Gronenborn, A.M.]]
+[[Category: Gronenborn, A M.]]
 [[Category: proteinase inhibitor(trypsin)]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Tue Nov 20 11:07:21 2007''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:48:09 2008''