Purification and characterization of a membrane-bound protein kinase from spinach thylakoids

A protein kinase was isolated from spinach thylakoid membranes by solubilization with octyl glucoside and cholate. The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, and sucrose density centrifugation, followed by affinity chromatography on either Affi-Gel blue (yielding denatured enzyme) or on histone cross-linked to Sepharose (yielding active enzyme). Electrophoresis on denaturing polyacrylamide gels, followed by staining with silver, revealed the kinase as a single band corresponding to an apparent molecular mass of 64 kDa. The active enzyme underwent autophosphorylation and could be detected by autoradiography following incubation with [gamma-32P]ATP and Mg2+ ion. The specific phosphotransferase activity of purified kinase was approximately 30 nmol of phosphate min-1 (mg protein)-1 with lysine-rich histone (III-S or V-S) as substrate; casein was phosphorylated at approximately 30% of this rate. The physiological substrate for the kinase is presumed to be light-harvesting chlorophyll a/b protein complex. In solubilized form, this was phosphorylated at approximately 10% of the rate observed with histone III-S as substrate, or 10-100 times slower than the estimated rate of phosphorylation of the light-harvesting complex in situ. Possible reasons for this shortfall are considered. The kinase is proposed as the principal effector of thylakoid protein phosphorylation and associated State transition phenomena.     

Plate 457. Mutisia Subspinosa Compositae

Mutisia subspinosa Cav. is described and illustrated and its relationships with other members of Mutisia sect. Guariruma (Cass.) Cabrera discussed. Notes on its cultivation are provided along with a historical insight into the collections of Née, made on the Malaspina expedition.     

Crusticorallina gen. nov., a nongeniculate genus in the subfamily Corallinoideae (Corallinales,Rhodophyta)

Molecular phylogenetic analyses of 18S rDNA (SSU) gene sequences confirm the placement of Crusticorallina gen. nov. in Corallinoideae, the first nongeniculate genus in an otherwise geniculate subfamily. Crusticorallina is distinguished from all other coralline genera by the following suite of morpho‐anatomical characters: (i) sunken, uniporate gametangial and bi/tetrasporangial conceptacles, (ii) cells linked by cell fusions, not secondary pit connections, (iii) an epithallus of 1 or 2 cell layers, (iv) a hypothallus that occupies 50% or more of the total thallus thickness, (v) elongate meristematic cells, and (vi) trichocytes absent. Four species are recognized based on rbcL, psbA and COI‐5P sequences, C. painei sp. nov., the generitype, C. adhaerens sp. nov., C. nootkana sp. nov. and C. muricata comb. nov., previously known as Pseudolithophyllum muricatum. Type material of Lithophyllum muricatum, basionym of C. muricata, in TRH comprises at least two taxa, and therefore we accept the previously designated lectotype specimen in UC that we sequenced to confirm its identity. Crusticorallina species are very difficult to distinguish using morpho‐anatomical and/or habitat characters, although at specific sites, some species may be distinguished by a combination of morpho‐anatomy, habitat and biogeography. The Northeast Pacific now boasts six coralline endemic genera, far more than any other region of the world.     

Kinetic evidence for involvement of two cytochrome b-563 hemes in photosynthetic electron transport

The effect of 2-(n-heptyl)-4-hydroxyquinoline N-oxide (HQNO) on the kinetics of cytochrome b-563 and cytochrome c² turnovers following single-turnover flashes was measured in isolated heterocysts. Low concentrations of HQNO (below 3 μM) blocked reoxidation of cytochrome b-563, whereas higher concentrations (above 5 μM) resulted in additional inhibition of cytochrome b-563 oxidation and also inhibited reduction of cytochrome b-563 and cytochrome c. Similar effects on cytochrome b-563 reduction and reoxidation were obtained with a combination of 5 μM HQNO and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (1–7 μM). In HQNO-inhibited heterocysts, cytochrome c reduction following a flash occurred in three phases with half-times of 0.5, 2.8 and 45 ms. The second phase nearly equalled the cytochrome b-563 reduction in half-time and magnitude. In the presence of HQNO, the reoxidation of cytochrome b-563 following two closely spaced actinic flashes displayed biphasic kinetics. The two phases correspond to reoxidation of cytochrome b-563 in which one or both of the cytochrome b-563 hemes in the cytochrome b–f complex are reduced. These results are interpreted in terms of a Q-loop in which HQNO, at low concentrations, blocks the site of rapid cytochrome b-563 reoxidation and at higher concentrations, also inhibits the site of electron donation by plastoquinol to the cytochrome b-f complex.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

624. DACTYLICAPNOS VENTII

Summary Dactylicapnos ventii (Khánh) Lidén is described and illustrated. Misidentification when this species was first introduced into cultivation has led to confusion with D. lichiangensis (Fedde) Hand.‐Mazz.