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(c) The tube and cylinder diagram to the right illus- trates schematically the potassium channel protein from a bacterium. This channel protein consists of four identical polypeptide chains each comprised of 119 residues. The cyan ribbon illustrates only two of the polypeptide chains. The relative positions of 4 α-helices, one from each poly- peptide chain, are shown as cylinders. The red sphere in the central part of the diagram shows the position of a potas- sium ion identified by X-ray structure analysis. A cesium ion (green sphere) was also found to be stabilized in the same position when cesium chloride was introduced into the crys- tals. The cylinders each represent an α-helix running from Tyr62 to Thr74. Considering the position of the potassium ion, in- dicate on one of the cylinders at which end of the cylinder residue Tyr62 is found and at which end residue Thr74 is found. Explain the basis of your answer? Ala23 Thr119 (d) The N- and C-terminal residues of one of the polypeptide chains are labeled. (The N-terminal residue is labeled Ala23 because the first 22 residues are disordered and are not identifiable in the electron density map.) Indicate the orientation, i.e., positive end and negative end, of the macrodipole of each of the two long helices. What can you state about their relative orientation to each other? (e) What is the length of each of the long helices belonging to the polypeptide chain with N- and C-terminal residues labeled?

(c) The tube and cylinder diagram to the right illus- trates schematically the potassium channel protein from a bacterium. This channel protein consists of four identical polypeptide chains each comprised of 119 residues. The cyan ribbon illustrates only two of the polypeptide chains. The relative positions of 4 α-helices, one from each poly- peptide chain, are shown as cylinders. The red sphere in the central part of the diagram shows the position of a potas- sium ion identified by X-ray structure analysis. A cesium ion (green sphere) was also found to be stabilized in the same position when cesium chloride was introduced into the crys- tals. The cylinders each represent an α-helix running from Tyr62 to Thr74. Considering the position of the potassium ion, in- dicate on one of the cylinders at which end of the cylinder residue Tyr62 is found and at which end residue Thr74 is found. Explain the basis of your answer? Ala23 Thr119 (d) The N- and C-terminal residues of one of the polypeptide chains are labeled. (The N-terminal residue is labeled Ala23 because the first 22 residues are disordered and are not identifiable in the electron density map.) Indicate the orientation, i.e., positive end and negative end, of the macrodipole of each of the two long helices. What can you state about their relative orientation to each other? (e) What is the length of each of the long helices belonging to the polypeptide chain with N- and C-terminal residues labeled?

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
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(c) The tube and cylinder diagram to the right illus- trates schematically the potassium channel protein from a bacterium. This channel protein consists of four identical polypeptide chains each comprised of 119 residues. The cyan ribbon illustrates only two of the polypeptide chains. The relative positions of 4 α-helices, one from each poly- peptide chain, are shown as cylinders. The red sphere in the central part of the diagram shows the position of a potas- sium ion identified by X-ray structure analysis. A cesium ion (green sphere) was also found to be stabilized in the same position when cesium chloride was introduced into the crys- tals. The cylinders each represent an α-helix running from Tyr62 to Thr74. Considering the position of the potassium ion, in- dicate on one of the cylinders at which end of the cylinder residue Tyr62 is found and at which end residue Thr74 is found. Explain the basis of your answer? Ala23 Thr119 (d) The N- and C-terminal residues of one of the polypeptide chains are labeled. (The N-terminal residue is labeled Ala23 because the first 22 residues are disordered and are not identifiable in the electron density map.) Indicate the orientation, i.e., positive end and negative end, of the macrodipole of each of the two long helices. What can you state about their relative orientation to each other? (e) What is the length of each of the long helices belonging to the polypeptide chain with N- and C-terminal residues labeled?
Transcribed Image Text:(c) The tube and cylinder diagram to the right illus- trates schematically the potassium channel protein from a bacterium. This channel protein consists of four identical polypeptide chains each comprised of 119 residues. The cyan ribbon illustrates only two of the polypeptide chains. The relative positions of 4 α-helices, one from each poly- peptide chain, are shown as cylinders. The red sphere in the central part of the diagram shows the position of a potas- sium ion identified by X-ray structure analysis. A cesium ion (green sphere) was also found to be stabilized in the same position when cesium chloride was introduced into the crys- tals. The cylinders each represent an α-helix running from Tyr62 to Thr74. Considering the position of the potassium ion, in- dicate on one of the cylinders at which end of the cylinder residue Tyr62 is found and at which end residue Thr74 is found. Explain the basis of your answer? Ala23 Thr119 (d) The N- and C-terminal residues of one of the polypeptide chains are labeled. (The N-terminal residue is labeled Ala23 because the first 22 residues are disordered and are not identifiable in the electron density map.) Indicate the orientation, i.e., positive end and negative end, of the macrodipole of each of the two long helices. What can you state about their relative orientation to each other? (e) What is the length of each of the long helices belonging to the polypeptide chain with N- and C-terminal residues labeled?
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