Question

6. (10 pts) Membrane spanning regions A. (2 pts) Why do proteins assume a secondary structure when they traverse the membrane? B. (2 pts) How would you predict the presence of a single membrane spanning a- helix? Be specific. C. (2 pts) What observation would make you conclude that the single membrane spanning a-helix is located in a sphingolipid raft?

PLEASE ANSWER ALL PARTS. THANK YOU!

Answer 1

ANSWER

6.

A.

The whole crystallised shape of LAT is still now not posted because it's miles nonetheless very tough to crystallise membrane proteins. Therefore, we can handiest predict viable secondary systems and features of LAT.

The protein structure homology-modeling servers that we used to examine the amino acid sequence of LAT are “Swiss-Model”, JPRED3 and Kyte-Doolittle.

B.

In theory, the membrane-spanning location is regularly an α-helix comprising of around 20 amino acid residues. When data at the 3-D structure is absent the presence of transmembrane α-helical segments in membrane protein can be predicted by seeking out amino acid sequences in hydrophobic regions (excessive hydropathy values)

C.

Peptide oligomerization triggered via hydrophobic mismatch and the presence of LDL cholesterol is probable to play a role within the biology of membrane proteins, for example, in signalling methods in which clustering of receptor proteins is associated with partitioning into raft-like domains. Because of the excess LDL cholesterol content and the long chains of the sphingolipids in these raft-like domains, they may be anticipated to be thicker than the surrounding membrane, in which the proteins might be specifically present as monomers. Here, less favourable interactions among the lipids and the receptor proteins may help to house the oligomerized shape into those raft domains.

D.

The lipid-water interface (LWI) place represents a unique physicochemical microenvironment in a membrane-bound machine in which the concentration of free water is much less and the residues present in this place are especially unstructured and offer possibilities of numerous non-covalent interactions via their aspect chains with specific components present in the lipid bilayer. The LWI-residues as the five amino acids stretch series on both aspects of the N-terminal and C-terminal ends of every TM helices.

E.

The other important structural element found in globular proteins is the β sheet. Historically, it becomes first found as the β or prolonged, shape of keratin fibers. Approximate know-how of the molecular shape worried was finished much earlier for the β than for the α structure because repeat distances along the fiber showed that the spine needs to be nearly fully prolonged, which did now not leave very much preference of conformation even if the info of spine geometry were not properly known. Astbury described the β shape in 1933 as straight, prolonged chains with alternating side-chain path and hydrogen bonds between adjacent antiparallel chains. Pauling and Corey (1951) described the perfect hydrogen-bonding styles for both antiparallel and parallel β sheet and also found out that the sheets were "pleated," with α-carbons successively a bit above and under the plane of the sheet. Some features of β structure, together with its function twist, were not recognized till after numerous β sheets had been seen in three-dimensional protein structures.