scholarly journals Ca2+- and calmodulin-dependent protein phosphorylation in rat lacrimal gland

1982 ◽  
Vol 202 (3) ◽  
pp. 799-802 ◽  
Author(s):  
D A Dartt ◽  
V J Guerina ◽  
M Donowitz ◽  
L Taylor ◽  
G W G Sharp
Keyword(s):  
Protein Phosphorylation ◽  
Protein Kinases ◽  
Lacrimal Gland ◽  
Binding Protein ◽  
Lacrimal Glands ◽  
Dependent Activity ◽  
Dependent Protein ◽  
Gland Function

Ca2+, in homogenized lacrimal glands, enhanced phosphorylation of several peptides. Phosphorylation of two of these peptides was further stimulated by addition of the Ca2+-binding protein calmodulin and decreased by trifluoperazine, an inhibitor of Ca2+-calmodulin-dependent activity. Thus, Ca2+-calmodulin-dependent protein kinases and their substrates are present in lacrimal gland and could have an important role in lacrimal-gland function.

Possible Roles for Protein Phosphorylation in Platelet Responses

1979 ◽  
Author(s):  
R.J. Haslam ◽  
J.E.B. Fox ◽  
S.E. Salama ◽  
J.A. Lynham
Keyword(s):  
Cyclic Amp ◽  
Protein Phosphorylation ◽  
Protein Kinases ◽  
Platelet Function ◽  
Subcellular Fractionation ◽  
Human Platelets ◽  
Type I ◽  
Sds Page ◽  
Dependent Protein ◽  
32P Incorporation

The relationships between the phosphorylation of specific platelet polypeptides and platelet function were studied using washed human platelets labelled by preincubation with [32p] Pi. Platelet polypeptides were separated by SDS-PAGE and 32P incorporation into them determined by autoradiography. Whereas induction of platelet aggregation alone did not affect protein phosphorylation, induction of the release reaction increased 3P incorporation into several polypeptides (P75,P47,P40,P27,P20,P19), including the P-light chain of platelet myosin (P20). These changes were inhibited by drugs that blocked Ca2 movements and may be due to activation of Ca2+-dependent protein kinases. Compounds that inhibited platelet function by increasing cyclic AMP (e.g. PCE1) also suppressed these reactions but, in addition, increased phosphorylation of other polypeptides (P50,P49,P36,P24,P22). Type I and Type II cyclic AMP-dependent protein kinases were present in platelets and may mediate Che latter effects of cyclic AMP. Subcellular fractionation of 32p-labelled platelets that had been exposed to PCE1 showed that P24 was present in membranes that could take up Ca2+ by an ATP-dependent mechanism. Membranes from PCE1-treated platelets took up Ca2+ more rapidly than control membranes. Thus, the cyclic AMP-dependent phosphorylation of P24 may stimulate the removal of Ca2+ from platelet cytosol and suppress Ca2+-dependent phosphorylation reactions necessary for release of granule constituents.

scholarly journals Molecular and biochemical characterization of a calcium/calmodulin-binding protein kinase from rice

2002 ◽  
Vol 368 (1) ◽  
pp. 145-157 ◽  
Author(s):  
Lei ZHANG ◽  
Bi-Feng LIU ◽  
Shuping LIANG ◽  
Russell L. JONES ◽  
Ying-Tang LU
Keyword(s):  
Protein Kinase ◽  
Protein Kinases ◽  
Biochemical Characterization ◽  
Catalytic Domain ◽  
Binding Protein ◽  
Enzymic Activity ◽  
Dependent Manner ◽  
Surface Plasmon Resonance Analysis ◽  
Calmodulin Binding ◽  
Dependent Protein

A Ca2+/calmodulin (CaM)-binding protein kinase from rice (Oryza sativa), OsCBK, has been characterized that lacks Ca2+-binding EF hands and has Ca2+/CaM-independent autophosphorylation and substrate-phosphorylation activity. OsCBK has all 11 subdomains of a kinase catalytic domain and a putative CaM-binding domain, and shares high identity with Ca2+-dependent-protein-kinase ('CDPK')-related protein kinases in plants. OsCBK bound CaM in a Ca2+-dependent manner as previously reported for Ca2+/calmodulin-dependent protein kinases in animals, but autophosphorylation and phosphorylation of histone IIIs were Ca2+/CaM-independent. Surface plasmon resonance analysis showed that OsCBK specifically bound CaM with high affinity (KD = 30nM). Capillary electrophoresis showed that phosphorylation of OsCBK occurred on serine and threonine residues. These data show that OsCBK is a serine/threonine protein kinase that binds Ca2+/CaM, but whose enzymic activity is independent of Ca2+/CaM. In situ hybridization showed that OsCBK is expressed in reproductive and vegetative tissues of rice and shows temporal and spatial changes during plant growth and development. OsCBK is highly expressed in zones of cell division and it is particularly abundant in sporogenous cells of the anther at meiosis.

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