caa a22 4500 477101100 CHVBK 20180405111541.0 cr unu---uuuuu 170330e19960201xx s 000 0 eng 10.1007/BF00206256 doi (NATIONALLICENCE)springer-10.1007/BF00206256 Hager A. Botanisches Institut, Universität Tübingen, Auf der Morgenstelle 1, D-72076, Tübingen, Germany aut Properties of a blue-light-absorbing photoreceptor kinase localized in the plasma membrane of the coleoptile tip region [Elektronische Daten] [A. Hager] The blue-light-sensing apical part of coleoptiles of grasses is responsible for the first positive phototropic bending reaction of this organ. The photoreceptor responsible has been shown to be localized to the plasma membrane (PM) of this tip region. An approximately 100-kDa protein moiety of this receptor is rapidly phosphorylated upon irradiation. Properties of this protein kinase reaction were studied in vitro by using PMs from the maize (Zea mays L.) coleoptile tip region: (i) The substrate for the blue-light-triggered phosphorylation of the 100-kDa protein was found to be ATP as well as GTP. However, the affinity of the involved protein kinase for the substrate GTP was lower than for ATP. (ii) Experiments were undertaken to find out whether a photoreceptor moiety acts as an autophosphorylating protein kinase or whether the photoreceptor protein, when activated by light, becomes the target of an extrinsic protein kinase. Two studied extrinsic protein kinases (50 and 55 kDa) of the coleoptile tip were found not to be involved in the lightdependent protein phosphorylation. The degree of phosphorylation of the 100-kDa protein on isolated plasma membranes upon irradiation at 0 °C was scarcely different from a reaction at 30 °C, in contrast to the background protein phosphorylations which decreased with decreasing temperature. This result points to an autophosphorylation mechanism at the receptor. (iii) In mixing experiments, solubilized membranes from maize coleoptiles were irradiated and added to unirradiated membrane proteins from pea (Pisum sativum L.) epicotyls followed by addition of [γ-32P]ATP. Unirradiated proteins from pea were not phosphorylated by light-activated (autophosphorylatable) maize protein kinases. (iv) It is suggested that the blue-light-sensitive photoreceptor localized to the PM of the phototropically active tip region of coleoptiles has an autophosphorylatable kinase domain which is able to use ATP or GTP as substrate. Springer-Verlag, 1996 Blue light nationallicence Coleoptile nationallicence Phosphorylation of proteins nationallicence Photoreceptor nationallicence Phototropism nationallicence Zea nationallicence PM : plasma membrane nationallicence Planta Springer-Verlag 198/2(1996-02-01), 294-299 0032-0935 198:2<294 1996 198 425 https://doi.org/10.1007/BF00206256 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00206256 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Hager A. Botanisches Institut, Universität Tübingen, Auf der Morgenstelle 1, D-72076, Tübingen, Germany aut NATIONALLICENCE 773 0- Planta Springer-Verlag 198/2(1996-02-01), 294-299 0032-0935 198:2<294 1996 198 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer