Hartshorn R T, Moore G R
Inorganic Chemistry Laboratory, University of Oxford, U.K.
Biochem J. 1989 Mar 1;258(2):595-8. doi: 10.1042/bj2580595.
The observation that 6 M-urea denatures horse ferricytochrome c in the pH range 4-6, but not horse ferrocytochrome c, has been exploited to determine the denaturation-induced proton uptake of ferricytochrome c. This is related to the pKa values of ionizable groups buried within the native protein. The data indicate that one of the haem propionic acid substituents of ferricytochrome c has a pKa of less than 4.5, whereas the other has a pKa of greater than 9.
6M尿素在pH值4 - 6范围内可使马高铁细胞色素c变性,但不能使马亚铁细胞色素c变性,这一现象已被用于测定高铁细胞色素c变性诱导的质子摄取。这与天然蛋白质中埋藏的可电离基团的pKa值有关。数据表明,高铁细胞色素c的一个血红素丙酸取代基的pKa小于4.5,而另一个的pKa大于9。