pThree large fragments of human serum albumin were produced by peptic digestion of the native protein [Geisow & Beaven (1977) Biochem. J. 161, 619-625]. Fragment P44 represents residues 1-386 and fragments P29 and P31 represent residues 49-307 and residues 308-584 respectively of the albumin molecule. The large N-terminal fragment P44 has a similar percentage of alpha-helix to stored defatted albumin, although the alpha-helix content of all the fragments is significantly less than that of freshly prepared albumin. The fragment P44 appears to account for all the binding of the hydrophobic probe 8-anilinonaphthalene-1-sulphonate to albumin. N-Acetyl-L-tryptophan binds to this fragment and displaces one of the bound molecules of 8-anilinonaphthalene-1-sulphonate. Bilirubin binds to fragments P44 and P29, and the complexes show similar circular-dichroism spectra to that of the complex between bilirubin and whole albumin. These results are in agreement with affinity-labeling work on albumin with reactive ligands where substitution occurs in the N-terminal region of the molecule. The sharp conformational transitional transition in albumin which is observed between pH4 and 3.5 was absent from the fragments. This isomerization, usually called the N-F transition, probably occurs in intact albumin as a result of the unfolding or separation of the C-terminal third of the protein from the remainder of the molecule./p
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机译：通过消化天然蛋白[Geisow＆amp; Co.，Ltd.，1986，J.Am.Chem.Soc。，37，2，3，4，5，6，7，8，9，9，9，9，8，9，8，9，8，9，8，9，8，9，8，8，8，8，9，8，9，8，9，8，9，8，8，8，8，8，8，9，9，9，8，8，8，9，8，9，8，9，9，9，9，9，7，7，8号人血清白蛋白大片段。 Beaven（1977）生物化学。 J. 161，619-625]。片段P44代表白蛋白分子的残基1-386，片段P29和P31代表白蛋白分子的残基49-307和残基308-584。大的N-末端片段P44具有与存储的脱脂白蛋白相似的α-螺旋百分比，尽管所有片段的α-螺旋含量均明显低于新鲜制备的白蛋白。片段P44似乎解释了疏水探针8-苯胺基萘-1-磺酸盐与白蛋白的所有结合。 N-乙酰基-L-色氨酸结合至该片段，并取代了8-苯胺基萘-1-磺酸盐的结合分子之一。胆红素与片段P44和P29结合，并且该复合物显示出与胆红素和整个白蛋白之间的复合物相似的圆二色性光谱。这些结果与具有反应性配体的白蛋白的亲和标记工作一致，其中取代发生在分子的N端区域。在片段中不存在在pH4至3.5之间观察到的白蛋白中的急剧构象过渡转变。这种异构化通常称为N-F过渡，可能是由于蛋白的C末端三分之一从分子的其余部分上解折叠或分离而在完整的白蛋白中发生的。
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