Vasudevan G, McDonald M J
Department of Chemsitry, College of Arts and Sciences, University of Massachusetts, Lowell 01854, USA.
J Protein Chem. 2000 Oct;19(7):583-90. doi: 10.1023/a:1007150318854.
The interaction of apohemoglobin with two heme derivatives, CN-protohemin and CN-deutero-hemin, was monitored at multiple Soret wavelengths (417-423 and 406-412 nm, respectively) in 0.05 M potassium phosphate buffer, pH 7.0, at 10 degrees C and revealed, as previously reported, a multiphasic kinetic reaction. Wavelength-dependent reactions were observed for both CN-protohemin and CN-deuterohemin derivatives with the alpha chain (bathochromic entity) displaying faster (4- to 7-fold) rates throughout the courses of both heme-binding reactions. The basis of this spectrally heterogeneous kinetic phenomenon could be deduced from molecular modeling studies of alpha- and beta-chain structures. Key differences in the number of stabilizing contacts of the two chains with the peripheral alpha propionyl 45(CE3); 58(E7); 61(E10) as well as the beta vinyl 38(C4); 71(E15); 106(G8) groups were found. Furthermore, RMS plots comparing apo- and heme-containing subunits reveal substantial structural disparities in the C-CD-F-FG helical regions of the alphabeta dimer interface.
在10℃的条件下于pH 7.0的0.05M磷酸钾缓冲液中，在多个Soret波长（分别为417 - 423纳米和406 - 412纳米）下监测载脂蛋白血红蛋白与两种血红素衍生物（氰化原卟啉和氰化次卟啉）的相互作用，结果如先前报道的那样，显示出多相动力学反应。对于氰化原卟啉和氰化次卟啉衍生物，均观察到了波长依赖性反应，在两种血红素结合反应过程中，α链（红移实体）的反应速率更快（快4至7倍）。这种光谱异质性动力学现象的基础可以从α链和β链结构的分子建模研究中推导出来。发现两条链与外周α-丙酰基45(CE3)、58(E7)、61(E10)以及β-乙烯基38(C4)、71(E15)、106(G8)基团的稳定接触数量存在关键差异。此外，比较载脂蛋白和含血红素亚基的RMS图显示，在αβ二聚体界面的C - CD - F - FG螺旋区域存在显著的结构差异。
