Redox dependence of the blue-light-induced phosphorylation of a 100-kDa protein on isolated plasma membranes from tips of coleoptiles (of Zea mays)

A blue-light-induced rapid phosphorylation of a 100-kDa protein localized in plasma membranes of phototropically sensitive tips of maize (Zea mays L.) coleoptiles was studied. Since, under in-vivo conditions or in a crude homogenate of tips, cytosolic ATP is the phosphate donor for the light-induced...

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Bibliographic Details
Published in:	Planta Vol. 190; no. 1; pp. 120 - 126
Main Authors:	Hager, A. (Tuebingen Univ. (Germany). Botanisches Inst.), Brich, M, Bazlen, I
Format:	Journal Article
Language:	English
Published:	Berlin Springer-Verlag 01-05-1993 Springer
Subjects:	Autoradiography Auxins Biological and medical sciences Cell biochemistry Cell membranes Cell physiology COLEOPTILE COLEOPTILES COLEOPTILOS Corn FOSFORILACION Fundamental and applied biological sciences. Psychology Irradiation Koleoptyle Lichtfarbe LIGHT LUMIERE LUZ Peas PHOSPHORYLATION Phosphorylierung Photons Photoreceptors Phototropismus Plant physiology and development POTENCIAL REDOX POTENTIEL REDOX Protein PROTEINAS PROTEINE PROTEINS REDOX POTENTIAL Redoxpotential TROPISME TROPISMO TROPISMS Zea ZEA MAYS Redox state Monocotyledones Phosphorylation Membrane protein Zea mays Phototropism Cereal crop Photoinduction Gramineae Angiospermae Plasma membrane Spermatophyta Blue light
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Summary:	A blue-light-induced rapid phosphorylation of a 100-kDa protein localized in plasma membranes of phototropically sensitive tips of maize (Zea mays L.) coleoptiles was studied. Since, under in-vivo conditions or in a crude homogenate of tips, cytosolic ATP is the phosphate donor for the light-induced phosphorylation of this protein, a subsequent in-vitro phosphorylation by [32P]ATP is prevented. However, in-vitro irradiation of microsomal membranes isolated from non-irradiated tips followed by a 1-min incubation with [32P]ATP resulted in a strong phosphorylation (labelling) of the 100-kDa plasma-membrane protein. This process was saturated by a 7-s light pulse (200 μmol photons·m-2·s-1). In the absence of [32P]ATP the capacity for in-vitro phosphorylation of the 100-kDa protein after a 30-s light pulse declined slowly within 60 min but could be reconstituted by a new light pulse in the presence of reducing compounds. Moreover, when plasma membranes which had been stored frozen were used, reducing compounds such as NADH, NADPH, ascorbate, glutathione or dithiotreithol enhanced the light-triggered in-vitro phosphorylation. These compounds were unable to elicit or enhance the phosphorylation in the dark. It is suggested that the transfer of (blue-light) excited electrons from the chromophore moiety of the receptor to the target (either the 100-kDa protein or the protein kinase itself) is facilitated when reducing compounds instantly eliminate the positive charge generated at the chromophore. The transferred electrons could finally alter the redox state and—or the conformation of either the 100-kDa protein, rendering it susceptible to the action of a protein kinase, or the protein kinase which would then be capable of phosphorylating the 100-kDa protein.
Bibliography:	F61 93G0435
ISSN:	0032-0935 1432-2048
DOI:	10.1007/bf00195683