Structural changes of human RNase L upon homodimerization investigated by Raman spectroscopy.
RNase L, a key enzyme in the host defense system, is activated by the binding of 2'-5'-linked oligoadenylates (2-5A) to the N-terminal ankyrin repeat domain, which causes the inactive monomer to form a catalytically active homodimer. We focused on the structural changes of human RNase L as a result of interactions with four different activators: natural 2-5 pA(4) and three tetramers with 3'-end AMP units replaced with ribo-, arabino- and xylo-configured phosphonate analogs of AMP (pA(3)X). The extent of the RNase L dimerization and its cleavage activity upon binding of all these activators were similar. A drop-coating deposition Raman (DCDR) spectroscopy possessed uniform spectral changes upon binding of all of the tetramers, which verified the same binding mechanism. The estimated secondary structural composition of monomeric RNase L is 44% α-helix, 28% β-sheet, 17% β-turns and 11% of unordered structures, whereas dimerization causes a slight decrease in α-helix and increase in β-sheet (ca. 2%) content. The dimerization affects at least three Tyr, five Phe and two Trp residues. The α-β structural switch may fix domain positions in the hinge region (residues ca. 336-363) during homodimer formation.
Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
Martin
M
Kříž
Jan
J
Snášel
Vladimír
V
Kopecký
Ondřej
O
Páv
Ivan
I
Rosenberg
Josef
J
Stěpánek
D000227:Adenine Nucleotides / Q000737:chemistry / Q000378:metabolism; D017089:Ankyrin Repeat; D004722:Endoribonucleases / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D011487:Protein Conformation; D055503:Protein Multimerization; D013059:Spectrum Analysis, Raman
D000227:Adenine Nucleotides; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease