Reaction Mechanism of (6-4) Photolyase

A cryptochrome/photolyase class of enzymes with single-stranded DNA-specific photolyase activity

“…The results in Fig. 2 show that whereas photolyase demonstrates some preference for single-stranded over double-stranded substrates, in agreement with previous reports (17,18), VcCry1 unequivocally repairs the dimer but only in ssDNA. Furthermore, the other Cry-DASH proteins from plant (AtCry3) and animal (XlCry-DASH) sources also demonstrated photoreactivation specifically toward ssDNA.…”

Structure and Function of Photolyase and in Vivo Enzymology: 50th Anniversary

“…Function-Biochemical and crystallographic data reveal that (6-4) photolyase has a reaction mechanism quite similar to that of PyrϽϾPyr photolyase (33)(34)(35)(36). The positively charged groove on the enzyme surface binds mainly through ionic bonds to the damaged strand and makes some weaker contacts with the complementary strand.…”

“…3B). Although some preliminary data seemed to support thermal formation of the oxetane intermediate (35), the recent crystallographic data strongly suggest that the oxetane intermediate may be a very short-lived transition state intermediate that forms photochemically (33).…”

“…The positively charged groove on the enzyme surface binds mainly through ionic bonds to the damaged strand and makes some weaker contacts with the complementary strand. The strong ionic interaction with the severely distorted DNA backbone facilitates the 180°flip-out of the (6-4) photoproduct into the active-site cavity (33,35).…”

Hetero-cycloreversions Mediated by Photoinduced Electron Transfer

“…57,58,59 In this context, reductive CR of a thietane has been achieved by intramolecular PET from a covalently linked flavin moiety ( Figure 14). 60 However, thietanes derived from 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 pyrimidine/thiopyrimidine dinucleotides are not enzymatically repaired, 61 which can be attributed to inefficient binding rather than to lack of ET-reactivity.…”