Refer to Lehninger Figure 11-9 (Intergral membrane proteins). Note: There is an
ID: 61971 • Letter: R
Question
Refer to Lehninger Figure 11-9 (Intergral membrane proteins). Note: There is an error in the figure. Types IV and V have their labels switched.
Imagine that the structural characteristics of a previously unknown integral membrane protein have just been published in a scientific journal. Given the following pieces of information from the journal article, determine the type of integral membrane protein that has just been discovered.
1)The first piece of information is that the protein does not have both a transmembrane helix and a glycosyl phosphatidylinositol anchor (GPI). This information eliminates type(s):
A) VI
B) I
C) V and VI
D) III
2)The second piece of information is that the protein is not anchored by a covalently linked lipid. This information eliminates type(s):
A) V
B) V and VI
C) I, II, III, IV, VI
D) none of the above
3) The third piece of information is that the protein has only a single membrane-spanning helix. This information eliminates type(s):
A) I and II
B) III
C) III and IV
4) The last piece of information is that the carboxy terminus is inside of the cell. This membrane protein must be type ___.
A) I
B) II
C) III
D) IV
E) V
F) VI
Inside HLNC00 Type VI Type IV Type V Outside NH, Type Ill Food Type II Typel FIGURE 11-9 Integral membrane proteins, For known proteins of the plasma membrane, the spatial relationships of protein domains to the lipid bilayer fall into six categories. Types I and II have a single trans membrane helix, the amino-teminal domain is outside the cell in type | proteins and inside in type II. Type Ill proteins have multiple tran smem bane helices in a single polypeptide. In type IV proteins, tran smem bane domains of several different polypeptides assemble to form a channel through the membrane. Type V proteins are held to the bilayer primarily by covalently linked lipids (see Fig. 1-15)and type VI proteins have both transmembrane helices and lipid anchors. In this figure, and in figures throughout the book, we represent trans membrane protein segments in their most likely conformations as a helices of six to seven turns. Sometimes these helices are shown simply as cylinders. As relatively few membrane protein structures have been deduced by X-ray crystallography, our representation of the extramem bane domains is arbitrary and not necessarily to scale.Explanation / Answer
* There must be some error in the question provided.
1. Except type VI, all other proteins have transmembrane helices. However, type VI proteins has only lipid anchor. Thererfore, the answer is (A) type IV
2. B. V and VI
3. C. III and IV
4. A. Type I