Distinction of the two binding sites of serum transferrin by resonance Raman spectroscopy

✍ Scribed by Sandra L. Mecklenburg; Anne B. Mason; Robert C. Woodworth; Robert J. Donohoe

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 252 KB
• Volume: 3
• Category: Article
• ISSN: 1075-4261
• DOI: 10.1002/(sici)1520-6343(1997)3:6<435::aid-bspy2>3.0.co;2-#

✦ Synopsis

The resonance Raman (RR) data for a variety of transferrin samples were investigated to explore differences between the two active sites. The excitation wavelength dependence of the RR data in the low energy shift region ( õ900 cm 01 ) for diferric transferrin (Fe 2 Tf) reveals extensive changes in the relative intensities for some of the peaks, indicating that the visible and near ultraviolet absorption of the Fe 2 Tf protein is composed of several distinct transitions. The identity of the low-energy vibrations was explored by comparison of the data from Fe 2 Tf, two different binding site mutants of the N-terminal site half transferrin molecule, Tf/2N, and Fe 2 Tf in which the normal binding site carbonate was replaced with C 18 O 20 3 . The higher energy RR spectra of the various samples are quite similar, whereas the low-energy band patterns are strongly influenced by the mutations and isotopic substitution. Comparison of the RR data obtained from Fe 2 Tf, Tf/2N, and C-terminal monoferric transferrin reveals that the intensities and energies of the modes below 900 cm 01 are different for the two binding sites. This result helps reveal an isolated electronic transition for the N-terminal active site near 365 nm, where laser excitation yields selective enhancement of the low-energy N-terminal modes.