Antiparallel B strands Parallel B strands +180 P Polypeptide Il helx +120 +60 -Left-handed a helk Right-handed - a hellx - 310 hellx -60 -120 - 180, 180 - 120 -60 +60 +120 +180 A FIGURE 6.9 A Ramachandran plot for poly-L-alanine. A map of this type can be used to describe the backbone conformation of any poly- peptide residue as well as the secondary structures of proteins. The coordinates are the values of the bond angles o and y, defined as in Figure 6.3. The white areas correspond to sterically allowed conforma- tions for poly-L-alanine (i.e., a peptide consisting of only L-Ala residues) based on theoretical predictions. The gray dots in the background show the observed o and u angles for over 10,000 alanine residues found in protein X-ray crystal structures. Although a left-handed a helix is theo- retically allowed, it is very rare; thus, we do not show a model for the structure. The circles with the following symbols correspond to the secondary structures discussed in the text: aR, right-handed a helix; 3, 310 helix; B, B strand; PI, polypeptide Il helix; aL, left-handed a helix. Data plot, courtesy of P. A. Karplus (Oregon State University).
Antiparallel B strands Parallel B strands +180 P Polypeptide Il helx +120 +60 -Left-handed a helk Right-handed - a hellx - 310 hellx -60 -120 - 180, 180 - 120 -60 +60 +120 +180 A FIGURE 6.9 A Ramachandran plot for poly-L-alanine. A map of this type can be used to describe the backbone conformation of any poly- peptide residue as well as the secondary structures of proteins. The coordinates are the values of the bond angles o and y, defined as in Figure 6.3. The white areas correspond to sterically allowed conforma- tions for poly-L-alanine (i.e., a peptide consisting of only L-Ala residues) based on theoretical predictions. The gray dots in the background show the observed o and u angles for over 10,000 alanine residues found in protein X-ray crystal structures. Although a left-handed a helix is theo- retically allowed, it is very rare; thus, we do not show a model for the structure. The circles with the following symbols correspond to the secondary structures discussed in the text: aR, right-handed a helix; 3, 310 helix; B, B strand; PI, polypeptide Il helix; aL, left-handed a helix. Data plot, courtesy of P. A. Karplus (Oregon State University).
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...
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Proteins
We generally tend to think of proteins only from a dietary lens, as a component of what we eat. However, they are among the most important and abundant organic macromolecules in the human body, with diverse structures and functions. Every cell contains thousands and thousands of proteins, each with specific functions. Some help in the formation of cellular membrane or walls, some help the cell to move, others act as messages or signals and flow seamlessly from one cell to another, carrying information.
Protein Expression
The method by which living organisms synthesize proteins and further modify and regulate them is called protein expression. Protein expression plays a significant role in several types of research and is highly utilized in molecular biology, biochemistry, and protein research laboratories.
Question
Polyglycine, a simple polypeptide, can form a helix with φ = -80°, ψ = +150°. From the Ramachandran plot (as shown), describe this helix with respect to handedness.
Transcribed Image Text:Antiparallel B strands
Parallel B strands
+180
P
Polypeptide
Il helx
+120
+60
-Left-handed
a helk
Right-handed -
a hellx
- 310 hellx
-60
-120
- 180,
180
- 120
-60
+60
+120
+180
A FIGURE 6.9 A Ramachandran plot for poly-L-alanine. A map of this
type can be used to describe the backbone conformation of any poly-
peptide residue as well as the secondary structures of proteins. The
coordinates are the values of the bond angles o and y, defined as in
Figure 6.3. The white areas correspond to sterically allowed conforma-
tions for poly-L-alanine (i.e., a peptide consisting of only L-Ala residues)
based on theoretical predictions. The gray dots in the background show
the observed o and u angles for over 10,000 alanine residues found in
protein X-ray crystal structures. Although a left-handed a helix is theo-
retically allowed, it is very rare; thus, we do not show a model for the
structure. The circles with the following symbols correspond to the
secondary structures discussed in the text: aR, right-handed a helix; 3,
310 helix; B, B strand; PI, polypeptide Il helix; aL, left-handed a helix.
Data plot, courtesy of P. A. Karplus (Oregon State University).
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