Question

You have identified a novel protein that associates with the plasma membrane. You do not know whether this protein is a peripheral or a transmembrane protein. You therefore analyze the primary amino acid sequence (listed in the three letter code) for the presence of a transmembrane domain.
Met - Asp - Leu - Lys - Ile - Pro - Gly - Val - Glu - Arg - Met - Phe - Leu - Ile - Ser - Lys - Gly - Thr - Asp - Tyr - His - Asn - Gln - Val - Met - Val - Gly - Pro - Asp - Glu - Ala - Ala - Ala - Val - Met - Arg - Trp - Cys - Met - Phe - Ile - Val - Val - Val - Thr - Val - Glu - Glu - Gly - Asp - Met - Val - Ala - Ile - Ile - Val - Leu - Pro - Lys - Arg - Trp - Tyr - Phe - Ala - Gln - Tyr - Ala - Val - Leu - Ile - Leu - Met - Ala - Trp - Leu - Val - Phe - Val - Ile - Leu - Ala - Arg - Lys - His - Ala - Val - Ile - Leu - Trp - Tyr - Ala - Gly - Gln - Gly - Asn - Arg - His - Cys - Lys - Met

How many potential transmembrane domains can you identify in this protein?

a) 0
b) 1
c) 2
d) 3
e) 4

Answer 1

Answer:

(e)

Explanation:

Transmembrane protein are proteins that are firmly associated with membranes because it is integrated along the length of bilayer lipid membrane. This kind of protein is made up of two kinds of amino acid, hydrophilic or polar amino acid and hydrophobic or non polar amino acid. while peripheral protein loosely associated with membrane, they are present on the surface which means they are not integrated in to the cell membrane and facing intercellular fluid. this is why it contains only hydrophilic amino acid.

The primary amino acid sequence contains hydrophobic amino acid which identifies the protein as transmembrane protein. These amino acid are methionine (Met), leucine(Leu), valine(Val), glycine(Gly), tryptophan(Trp), isoleucine(Ile), phenylalanine(Phe), proline(Pro) and alanine(Ala)