Abstract
The spectral properties of peptides generated from etiolated-Avana, 124-kDa (kilodalton) phytochrome by endogenous protease(s) have been studied to assess the role of the amino-terminal and the carboxyl-terminal domains in maintaining the proper interaction between protein and chromophore. The amino-terminal, 74-kDa chromopeptide, a degradation product of the far-red absorbing form of the pigment (Pfr), is shown to be spectrally similar to the 124-kDa, undegraded molecule. The minimum and maximum of the difference spectrum (Pr-Pfr) are 730 and 665 nm, respectively, and the spectral-change ratio is unity. Also, like undegraded, 124-kDa phytochrome, the 74-kDa peptide exhibits minimal dark reversion. These data indicate that the 55-kDa, carboxyl-terminal half of the polypeptide does not interact with the chromophore and may not have a role in the structureal integrity of the amino-terminal domain. The 64-kDa chromopeptide can be generated directly from the 74-kDa species by cleavage of 10 kDa from the amino terminus upon incubation of this species as Pr. Accompanying this conversion are changes in the spectral properties, namely, a shift in the difference spectrum minimum to 722–724 nm and a tenfold increase in the capacity for dark reversion. These data indicate that the 6–10 kDa, amino-terminal segment continues to function in its role of maintaining proper chromophore-protein interactions in the 74-kDa peptide as it does in the undegraded molecule. Conversely, removal of this segment upon proteolysis to the 63-kDa species leads to aberrant spectral properties analogous to those observed when this domain is lost from the full-length, 124-kDa molecule, resulting in the 118/114-kDa degradation products. The data also show that photoconversion of the 74-kDa chromopeptide from Pfr to Pr exposes proteolytically susceptible sites in the same way as in the 124-kDa molecule. Thus, the separated, 74-kDa amino-terminal domain undergoes a photoinducible conformational change comparable to that in the intact molecule.
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Abbreviations
- Da:
-
dalton
- Pfr :
-
far-red-absorbing from of phytochrome
- PMSF:
-
phenylmethylsulfonyl fluoride
- Pr :
-
red-absorbing form of phytochrome
- R:
-
red light
- FR:
-
lar-red light
- ΔA r/ΔA fr :
-
spectral change ratio
- λ FRmax :
-
peak maximum (nm) of Pfr absorbance
References
Bolton, G.W., Quail P.H. (1982) Cell-free synthesis of phytochrome apoprotein. Planta 155, 212–217
Daniels, S.M., Quail, P.H. (1984) Monoclonal antibodies to three separate domains on 124-kilodalton phytochrome from Avena. Plant Physiol. 76, 662–626
Gardner, G., Pike, C.S., Rice, H.V., Briggs, W.R. (1971) “Disaggregation” of Phytochrome in vitro — a consequence of proteolysis. Plant Physiol. 48, 686–693
Hershey, H.P., Barker, R.F., Colbert, J.T., Lissemore, J.L., Quail, P.H. (1985) Phytochrome: Molecular properties, feedback regulation of mRNA levels and genomic clone isolation. In: Molecular form and function of the plant genome, in press. van Vloten-Doting, L. ed. Plenum Press, New York
Hunt, R.E., Pratt, L.H. (1979) Phytochrome immunoaffinity purification. Plant Physiol. 64, 322–326
Jones, A.M., Vierstra, R.D., Daniels, S.M., Quail, P.H. (1984) Peptide mapping of 124-kD, oat phytochrome. (Abstr.) Plant Physiol. 75, Suppl., 73
Pike, C.S., Briggs, W.R. (1972) The dark reactions of rye phytochrome in vivo and in vitro. Plant Physiol. 49, 514–520
Pratt, L.M. (1982) Phytochrome: The protein moiety. Annu. Rev. Plant Physiol. 33, 557–582
Shropshire, W., Jr., Mohr, H. (1983) Photomorphogenesis. Encyclopedia of plant physiology, N.S., vol. 16A, B. Springer, Berlin Heidelberg New York
Tokuhisa, J.G., Daniels, S.M., Quail, P.H. (1985) Spectral and immunochemical evidence for two distinct molecular species of phytochrome in light-grown Avena sativa L. Planta 164, 321–332
Vierstra, R.D., Cordonnier, M.-M., Pratt, L.H., Quail, P.H. (1984) Native phytochrome: immunoblot analysis of relative molecular mass and in-vitro proteolytic degradation for several plant species. Planta 160, 521–528
Vierstra, R.D., Quail, P.H. (1982) Proteolysis alters the spectral properties of 124 kdalton phytochrome from Avena. Planta 156, 158–165
Vierstra, R.D., Quail, P.H. (1983a) Photochemistry of 124 kilodalton Avena phytochrome in vitro. Plant Physiol. 72, 264–267
Vierstra, R.D., Quail, P.H. (1983b) Purification and initial characterization of 124-kilodalton phytochrome from Avena. Biochemistry 22, 2498–2505
Vierstra, R.D., Quail, P.H. (1985) Spectral chracterization and proteolytic mapping of native, 120-kilodalton phytochrome form Cucurbita pepo L. Plant Physiol. 77, 990–998
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Jones, A.M., Vierstra, R.D., Daniels, S.M. et al. The role of separate molecular domains in the structure of phytochrome from etiolated Avena sativa L.. Planta 164, 501–506 (1985). https://doi.org/10.1007/BF00395966
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DOI: https://doi.org/10.1007/BF00395966