Z,E ISOMERIZATION OF THE ALPHA-84 PHYCOVIOLOBILIN CHROMOPHORE OF PHYCOERYTHROCYANIN FROM MASTIGOCLADUS-LAMINOSUS INVESTIGATED BY FOURIER-TRANSFORM INFRARED DIFFERENCE SPECTROSCOPY
H. Foerstendorf et al., Z,E ISOMERIZATION OF THE ALPHA-84 PHYCOVIOLOBILIN CHROMOPHORE OF PHYCOERYTHROCYANIN FROM MASTIGOCLADUS-LAMINOSUS INVESTIGATED BY FOURIER-TRANSFORM INFRARED DIFFERENCE SPECTROSCOPY, FEBS letters, 402(2-3), 1997, pp. 173-176
The photoreaction of the phycoviolobilin (PVB) chromophore-containing
part of phycoerythrocyanin (PEC) from Mastigocladus laminosus was inve
stigated by Fourier-transform infrared spectroscopy (FT-IR). Differenc
e spectra between the parent states P566 and P507 mere obtained in (H2
O)-H-1 and 2H(2)O for the first time. The spectra are generally charac
terised by large changes in the range between 1710 and 1590 cm(-1) and
by a strong difference band around 1270 cm(-1). In order to study the
influence on the PVB chromophore upon aggregation, spectra of the alp
ha-subunit and the (a beta)(3) trimer are compared, showing distinct d
ifferences which may be of relevance for the chromophore-protein and p
rotein-protein interactions. The difference spectra demonstrate many s
imilarities to the spectra recently obtained for the P-r --> meta-R(c)
transition of phytochrome [Foerstendorf et al. (1996) Biochemistry 35
, 10793-10799]. In particular, a band around 1710 cm(-1) which was ten
tatively assigned to the C = O stretch of ring d is also observed in t
he spectra of PEC. It strongly supports this identification and the de
duced molecular interpretation on the protonation state of the chromop
hore.