A. series of small amino acids can contribute to a flexible linker between domai

Question

A. series of small amino acids can contribute to a flexible linker between domains in a fusion protein. Which amino acid has the smallest side chain? Explain your answer

B. An antibody is composed of several polypeptides. The polypeptides are covalently attached to one another. Which amino acid mediates these attachments? Explain your answer ?

C. Histones are an important component of chromatin. These proteins interact with the phosphates of DNA. Which amino acids could mediate these interactions? Explain your answer ?

D. Protein phosphorylation can serve as a molecular switch during cell signaling. Which amino acids can be phosphorylated on their side chains? Explain your answer ?

Explanation / Answer

A. Since glycine has 2 hydrogen atoms, one each on the parent and side chain, it's the only symmetrical and thus achiral amino acid. Since hydrogen is non-polar, glycine is a hydrophobic amino acid. The Hydrogenside-chain makes glycine the smallest amino acid.

B.The two heavy chains are linked to each other by disulfide bonds.This linkage is provided by sulfur containing amino acid called cysteine which is very good in forming disulfide linkages.

C. As phosphates of DNA form a negatively charged structure and histone proteins join this DNA. This interaction is made possible by positively charged amino acids like arginine and lysine.

D.The amino acids most commonly phosphorylated are serine, threonine, and tyrosine in eukaryotes(OWING TO THEIR OH GROUPS), and histidine in prokaryotes, which play important and well-characterized roles in signaling pathways and metabolism. However, many other amino acids can also be phosphorylated, including arginine, lysine, and cysteine.

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