题目

Which of the following statements about protein structure is correct?A. Proteins consisting of one polypeptide can have quaternary structure.B. The formation of a disulfide bond in a protein requires that the two participating cysteine residues be adjacent to each other in the primary sequence of the protein.C. The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunits.D. The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure.E. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.

Which of the following statements about protein structure is correct?

A. Proteins consisting of one polypeptide can have quaternary structure.

B. The formation of a disulfide bond in a protein requires that the two participating cysteine residues be adjacent to each other in the primary sequence of the protein.

C. The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunits.

D. The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure.

E. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.

题目解答

答案

E. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.

解析

本题主要考查蛋白质结构的相关知识，解题思路是对每个选项所涉及的蛋白质结构特点进行逐一分析判断。

  • 选项A：
    • 蛋白质的四级结构是指由两条或两条以上具有独立三级结构的多肽链通过非共价键相互结合而成的聚合体结构。
    • 所以仅由一条多肽链组成的蛋白质不可能具有四级结构，A选项错误。
  • 选项B：
    • 蛋白质中形成二硫键的两个半胱氨酸残基在一级结构中不一定是相邻的。
    • 它们可以在多肽链折叠过程中靠近并形成二硫键，B选项错误。
  • 选项C：
    • 蛋白质四级结构的稳定性主要是靠亚基间的非共价键（如氢键、离子键、疏水作用等）维持的。
    • 虽然也可能存在共价键，但不是主要因素，C选项错误。
  • 选项D：
    • 蛋白质的变性通常是指其空间结构被破坏，但在某些情况下，变性是可逆的。
    • 例如，在一定条件下，去除变性因素后，蛋白质可以恢复其二级和三级结构，D选项错误。
  • 选项E：
    • 蛋白质一级结构中氨基酸的特定序列包含了蛋白质正确折叠的信息。
    • 这是因为氨基酸的侧链性质决定了它们之间的相互作用，从而引导多肽链折叠成特定的二级、三级和四级结构，E选项正确。