TY - JOUR
T1 - Small-angle X-ray scattering studies on the macromolecular structure of the red-light-absorbing form of 121 kDa pea phytochrome and its 114 kDa chromopeptide
AU - Tokutomi, Satoru
AU - Kataoka, Mikio
AU - Sakai, Jun
AU - Nakasako, Masayoshi
AU - Tokunaga, Fumio
AU - Tasumi, Mitsuo
AU - Furuya, Masaki
N1 - Funding Information:
We express our sincere thanks to Dr. T. Ueki for encouraging this study, Dr. K.T. Yamamoto for useful discussion, Dr. Y. Amemiya and Dr. K. Kobayashi for technical advice, Dr. A. Nagatani for supplying the monoclonal antibody, Ms. Y. Tsuge for technical assistance and Dr. R. Wayne for correcting the English of the manuscript. This research was supported in part by Grants-in-Aid to S.T. (62580225), F.T. (62621001), and M.F. (62621001) from the Ministry of Education, Science and Culture and has been performed under the approval of the Photon Factory Program Ad-visary Committee (Proposal No. 86-106).
PY - 1988
Y1 - 1988
N2 - The macromolecular structure of 121 kDa pea phytochrome and its 114 kDa chromopeptide was studied by small-angle X-ray scattering (SAXS) and steric exclusion column chromatography. The molecular mass of the 114 kDa chromopeptide in the red-light-absorbing form (Pr) was determined to be 228 kDa in 100 mM potassium phosphate and 1 mM EDTA (pH 7.8) by SAXS, indicating that the chromopeptide is a dimer. The radius of gyration (Rg) of the chromopeptide was determined to be 53.8 Å by Guinier analysis of SAXS. The molecular mass of a sphere with an Rg of 53.8 Å is calculated to be 1140 kDa, which is far greater than the observed molecular mass for the 114 kDa chromopeptide. The discrepancy comes from the deviation of the molecular shape from a sphere and/or the dense distribution of electrons in the marginal area of the molecule. The apparent molecular mass of the chromopeptide was determined to be 314-318 kDa from steric exclusion column chromatography, indicating a nonglobular molecular shape. Assuming the overall shape is an ellipsoid of revolution, a prolate one (a = 24, b = 115 A ̊ and an oblate one (a = 85, b = 9 A ̊), where a and b are the equatorial diameter and the half-axial length, respectively, are calculated to have an Rg of 53.8 Å and a molecular mass of 228 kDa. The Rg of the 121 kDa phytochrome was 54.0 Å, suggesting that the terminal polypeptide(s), which is iacking in the 114 kDa chromopeptide, contributes only slightly to the molecular dimension. The apparent molecular mass of the chromopeptide increased to 321-324 kDa after red-light irradiation, indicating that the far-red-light-absorbing form (Pfr) of the chromopeptide has a different molecular dimension from that of Pr. The Guinier analysis of the SAXS of the chromopeptide in Pfr, however, was not successful, owing to the low content of Pfr and the aggregation after saturating red-light irradiation.
AB - The macromolecular structure of 121 kDa pea phytochrome and its 114 kDa chromopeptide was studied by small-angle X-ray scattering (SAXS) and steric exclusion column chromatography. The molecular mass of the 114 kDa chromopeptide in the red-light-absorbing form (Pr) was determined to be 228 kDa in 100 mM potassium phosphate and 1 mM EDTA (pH 7.8) by SAXS, indicating that the chromopeptide is a dimer. The radius of gyration (Rg) of the chromopeptide was determined to be 53.8 Å by Guinier analysis of SAXS. The molecular mass of a sphere with an Rg of 53.8 Å is calculated to be 1140 kDa, which is far greater than the observed molecular mass for the 114 kDa chromopeptide. The discrepancy comes from the deviation of the molecular shape from a sphere and/or the dense distribution of electrons in the marginal area of the molecule. The apparent molecular mass of the chromopeptide was determined to be 314-318 kDa from steric exclusion column chromatography, indicating a nonglobular molecular shape. Assuming the overall shape is an ellipsoid of revolution, a prolate one (a = 24, b = 115 A ̊ and an oblate one (a = 85, b = 9 A ̊), where a and b are the equatorial diameter and the half-axial length, respectively, are calculated to have an Rg of 53.8 Å and a molecular mass of 228 kDa. The Rg of the 121 kDa phytochrome was 54.0 Å, suggesting that the terminal polypeptide(s), which is iacking in the 114 kDa chromopeptide, contributes only slightly to the molecular dimension. The apparent molecular mass of the chromopeptide increased to 321-324 kDa after red-light irradiation, indicating that the far-red-light-absorbing form (Pfr) of the chromopeptide has a different molecular dimension from that of Pr. The Guinier analysis of the SAXS of the chromopeptide in Pfr, however, was not successful, owing to the low content of Pfr and the aggregation after saturating red-light irradiation.
KW - Conformational change
KW - Photoreceptor protein
KW - Phytochrome
KW - Protein conformation
KW - Radius of gyration
KW - Small-angle X-ray scattering
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U2 - 10.1016/0167-4838(88)90038-6
DO - 10.1016/0167-4838(88)90038-6
M3 - Article
AN - SCOPUS:0013544056
SN - 0167-4838
VL - 953
SP - 297
EP - 305
JO - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
JF - Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
IS - C
ER -