BioPHYSICAL chemistry

nucleotide is bound at a distant location containing two cysteine residues,

which that are oxidized as part of the enzymatic cycle, transiently forming

thiyl radicals. These radicals can be observed only when the intermediate

states are trapped.

370 PART 2 QUANTUM MECHANICS AND SPECTROSCOPY

Fe

Y Y

SH

Catalytic

site

B1

subunit

B2

subunit

Substrate-

specificity

site

Overall

activity

site

SH

SH SH

FeFe Fe

OO

Figure 16.27A model of

ribonucleotide reductase

showing the position

of the tyrosine radical

relative to the iron

cofactor and active site.

References and further reading

Allen, J.W.A., Watmough, N.J., and Ferguson, S.J.
(2000) A switch in heme axial ligation prepares
Paracoccus pantotrophus cytochrome cd 1 for catalysis.
Nature Structural Biology 7 , 885 – 8.
Gubitz, A.K., Feng, W., and Dreyfuss, G. (2004) The
SMN complex. Experimental Cell Research 296 , 51– 6.
Hakumaki, J.M. and Brindle, K.M. (2003) Techniques:
visualizing apoptosis using nuclear magnetic reson-
ance. Trends in Pharmacological Sciences 24 , 146 – 9.
Holzbaur, E.L.F. (2004) Motor neurons rely on motor
proteins. Trends in Cell Biology 14 , 233 – 40.
Lefebvre, S., Burglen, L., Reboullet, S. et al. (1995)
Identification and characterization of a spinal mus-
cular atrophy determining gene. Cell 80 , 155 – 65.
Lorson, C.L., Strasswimmer, J., Yao, L.M. et al. (1998)
SMN oligomerization defects correlates withspinal
muscular atrophy severity. Nature Genetics 19 , 63 – 7.
McDermott, A.E. (2004) Structural and dynamic stud-
ies of proteins by solid-state NMR spectroscopy:
rapid movement forward. Current Opinion in Struc-
tural Biology 14 , 554 – 61.

Meister, G., Eggert, C., and Fischer U. (2002) SMN-

mediated assembly of RNPs: a complex story.

Trends in Cell Biology 12 , 472– 8.

Nakahara, K., Hayashi, T., Konishi, S., and

Miyashita, Y. (2002) Functional MRI of macaque

monkeys performing a cognitive set-shifting task.

Science 295 , 1532–6.

Riek, R., Pervushin, K., and Wüthrich, K. (2000)

TROSY and CRINEPT:NMR with large molecular

and supramolecular structures in solution. Trends

in Biochemical Sciences 25 , 462– 8.

Selenko, P., Sprangers, R., Stier, G., Buhler, D.,

Kischer, U., and Sattler, M. (2001) SMN Tudor

domain structure and its interaction with the Sm

proteins. Nature Structural Biology 8 , 27–31.

Sprangers, R. and Kay, L.E. (2007) Quantitive

dynamics and binding studies of the 20S proteo-

some by NMR. Nature 445 , 618–22.

Staunton, D. Owen, J., and Campbell, I.D. (2003)

NMR and structural genomics. Accounts of Chemical

Research 36 , 207– 14.