Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 32, Problem 11P
Interpretation Introduction
Interpretation:
The reason for use of alpha helices in the membrane-spanning for the G-protein-coupled receptors needs to be explained.
Concept Introduction :
The structure of alpha-helix is a polypeptide chain like a coiled rod giving a spring like structure. These polypeptide chains are bonded together with hydrogen bonds. The beta strands are responsible for bonding in beta-pleated sheets where they linked in lateral manner with hydrogen bonds resulting formation of a backbone. The number of amino acids involved in beta strand or chain formation is from 3-10.
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Identify the following membrane associated proteins based on their structure: (a) tetramers of identical subunits, each with six membrane spanning α helices; (b) trimers of identical subunits, each with 16 β sheets forming a barrel like structure.
The Structure of the acetylcholine receptor is shown below:
A. Knowing the amino acid sequence of this protein, what tool would you use to identify the membrane-spanning region? Explain how it works.
Proteins that span the biological membrane bilayers often contain α-helices and b-barrels.
(a) Given that the insides of membranes are highly hydrophobic, predict what type of amino acyl residues would be found in a single alpha-helix that is spanning a membrane – draw a diagram to illustrate the arrangement of the R-groups within the membrane bilayer.
(b) Using a drawing, illustrate the R-group arrangement in the membrane-spanning region of a channel protein for water transport if the channel was made of:
six alpha-helices
six beta-strands
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