Characterization of argininosuccinate lyase (EC 4.3.2.1) from Chlamydomonas reinhardtii.

We have isolated and characterized argininosuccinate lyase (ASL; EC 4.3.2.1) from the photosynthetic green alga, Chlamydomonas reinhardtii. The general properties of Chlamydomonas ASL are very similar to those described previously for ASLs from phylogenetically diverse organisms. The algal ASL has a native Mr, determined by gel-filtration chromatography, of 218,000 +/- 25,000, and a pI of 5.4-5.6. The Km for argininosuccinate at 37 degrees C and pH 7.5 is 0.26 mM. The subunit Mr of Chlamydomonas ASL is approx. 50,000, determined by SDS/polyacrylamide-gel electrophoresis, in contrast with a previously reported value of 39,000. Rabbit antisera prepared against the Mr-50,000 protein completely abolished ASL activity in vitro. In contrast, serum prepared against the Mr-39,000 protein was ineffective in inhibiting ASL activity. Despite the general similarity of the physical properties of Chlamydomonas ASL and those of other ASLs, antiserum raised against the algal ASL did not cross-react with ASL preparations from Escherichia coli, Saccharomyces cerevisiae or bovine liver.     

Photosynthetic Electron Transport Chain of Chlamydomonas reinhardi. IV. Purification and Properties of Plastocyanin

The copper protein plastocyanin has been found to be an essential component of the photosynthetic electron transport chain of Chlamydomonas reinhardi, and in this paper we describe a method for its isolation and purification from the wild-type strain. In addition, we describe some of its properties and compare them with those reported for spinach plastocyanin.     

Messenger RNA of the large subunit of ribulose-1,5-bisphosphate carboxylase from Chlamydomonas reinhardi. Isolation and properties.

Polysomes specifically synthesizing the large subunit of ribulose-1,5-bisphosphate carboxylase were isolated from Chlamydomonas reinhardi cells by the indirect immunoprecipitation method. Electrophoretic analysis showed that the immunoprecipitated polysomes were of chloroplast origin. The mRNA coding for the large subunit which was purified from immunoprecipitated polysomes migrated at the 19-S position on sucrose density gradients, and its molecular weight was estimated to be 7.3 x 10(5) by acid-urea/agarose gel electrophoresis. The mRNA was translated in vivo with a cell-free protein-synthesizing system derived from Escherichia coli to give full-length large-subunit polypeptides.     

Citrate lyase from Klebsiella pneumoniae. The complete primary structure of the acyl lyase subunit

The primary structure of the beta-subunit (acyl lyase subunit) of citrate lyase from Klebsiella pneumoniae (ATCC 13,882) was determined with protein chemical methods. The polypeptide chain consists of 289 amino acid residues and has a molecular mass of 31,352 Da. The two half-cystine residues of the subunit are present as cysteines and not involved in disulfide bridges. The sequence shows no homology to known sequences of proteins or nucleic acids and reads (sequence; see text)     

The induction of allophanate lyase during the vegetative cell cycle in light-synchronized cultures of Chlamydomonas reinhardi.

Allophanate lyase can be induced by urea or acetamide 20-40-fold within 4 h in NH4 + -deprived cultures of Chlamydomonas reinhardi. In light-synchronized cultures, allophanate lyase induction appeared to be limited to the light phase of the cell cycle, provided that culture samples were induced under ongoing illumination conditions (i.e. light induction of light phase cells and dark induction of dark phase cells). However, when culture samples were induced under constant light conditions this cell cycle pattern was abolished. Light was found to be required for allophanate lyase induction and this was shown to be due, in part, to the light requirement for inducer uptake. The relationship between allophanate lyase induction and gametogenesis is discussed.     

Nitro analogs of substrates for argininosuccinate synthetase and argininosuccinate lyase

The nitro analogs of aspartate and argininosuccinate were synthesized and tested as substrates and inhibitors of argininosuccinate synthetase and argininosuccinate lyase, respectively. The Vmax for 3-nitro-2-aminopropionic acid was found to be 60% of the maximal rate of aspartate utilization in the reaction catalyzed by argininosuccinate synthetase. Only the nitronate form of this substrate, in which the C-3 hydrogen is ionized, was substrate active, indicating a requirement for a negatively charged group at the beta carbon. The V/K of the nitro analog of aspartate was 85% of the value of aspartate after correcting for the percentage of the active nitronate species. The nitro analog of argininosuccinate, N3-(L-1-carboxy-2-nitroethyl)-L-arginine, was a strong competitive inhibitor of argininosuccinate lyase but was not a substrate. The pH dependence of the observed pKi was consistent with the ionized carbon acid (pK = 8.2) in the nitronate configuration as the inhibitory material. The pH-independent pKi of 2.7 microM is 20 times smaller than the Km of argininosuccinate at pH 7.5. These results suggest that the tighter binding of the nitro analog relative to the substrate is due to the similarity in structure to a carbanionic intermediate in the reaction pathway.     

Three-dimensional structure of the argininosuccinate lyase frequently complementing allele Q286R.

Argininosuccinate lyase (ASL) catalyzes the reversible breakdown of argininosuccinate to arginine and fumarate, a reaction involved in the biosynthesis of arginine in all species and in the production of urea in ureotelic species. In humans, mutations in the enzyme result in the autosomal recessive disorder argininosuccinic aciduria. Intragenic complementation has been demonstrated to occur at the ASL locus, with two distinct classes of ASL-deficient strains having been identified, the frequent and high-activity complementers. The frequent complementers participate in the majority of the complementation events observed and were found to be either homozygous or heterozygous for a glutamine to arginine mutation at residue 286. The three-dimensional structure of the frequently complementing allele Q286R has been determined at 2.65 A resolution. This is the first high-resolution structure of human ASL. Comparison of this structure with the structures of wild-type and mutant duck delta1 and delta2 crystallins suggests that the Q286R mutation may sterically and/or electrostatically hinder a conformational change in the 280's loop (residues 270-290) and domain 3 that is thought to be necessary for catalysis to occur. The comparison also suggests that residues other than R33, F333, and D337 play a role in maintaining the structural integrity of domain 1 and reinforces the suggestion that residues 74-89 require a particular conformation for catalysis. The electron density has enabled the structure of residues 6-18 to be modeled for the first time. Residues 7-9 and 15-18 are in type IV beta-turns and are connected by a loop. The conformation observed is stabilized, in part, by a salt bridge between the side chains of R12 and D18. Although the disease causing mutation R12Q would disrupt this salt bridge, it is unclear why this mutation has such a significant effect on the catalytic activity as residues 1-18 are disordered in all other delta-crystallin structures determined to date.     

Colchicine-resistant mutants of Chlamydomonas reinhardi

Five colchicine-resistant mutant strains of Chlamydomonas reinhardi have been isolated. In colchicine-free medium they all have abnormally long cell doubling times and tend to occur within palmella envelopes, rather than as free-swimming cells. Zygote germination of all the mutants is abnormal, but crosses with wild type suggest that resistance is in each case due to a Mendelian mutation. It is suggested, though not proved, that the mutations may affect microtubular structures.     

Extracellular phosphatases of Chlamydomonas reinhardi and their regulation.

Chlamydomonas reinhardi, cultured under normal growth conditions, secreted significant amounts of protein and carbohydrates but not lipids or nucleic acids. A fivefold increase in light intensity led to a tenfold increase in secreted protein and carbohydrate. Among the proteins secreted was acid phosphatase with a pH optimum at 4.8 like the enzyme in the cells. Phosphorus depleted algae grown on minimal orthophosphate contained and secreted both acid and alkaline phosphatase. The pH optimum of the intracellular alkaline phosphatase was 9.2. When phosphorus-depleted cells were grown with increasing orthophosphate, intra- and extracellular alkaline phosphatase was almost completely repressed and intra- and extracellular acid phosphatase was partially repressed. Extracellular acid and alkaline phosphatase increased with the age of the culture. Electrophoresis indicated only one acid and one alkaline phosphatase in phosphorus-satisfied and phosphorus-depleted cells. Chlamydomonas cells suspended in an inorganic salt solution secreted only acid phosphatase; the absence of any extr-cellular cytoplasmic marker enzyme indicated that there was little, if any, autolysis to account for the extracellular acid enzyme. Phosphorus-depleted cells were able to grow on organic phosphates as the sole source of orthophosphate. Ribose-5-phosphate was the best for cell multiplication, and its utility was shown to be due to the cell's ability to use the ribose as well as the orthophosphatase for cell multiplication.     

Amide metabolism of Chlamydomonas reinhardi

Chlamydomonas reinhardi can utilise the lower aliphatic amides (C₁–C₄) as nitrogen sources. Of these only acetamide can serve as a sole carbon source. The acetamide analogue F-acetamide kills cells after conversion to F-acetate and F-citrate. This conversion is controlled by exogenous ammonia and, in part, acetate levels. Only one enzyme and one active site are involved in acetamidase function. Enzymatic analysis indicates an increased substrate range as compared to the growth — supported range, indicating uptake, toxicity or metabolic control restrictions.Abbreviations TCA trichloroacetic acid - TAP tris-acetate-phosphate medium - MIC mimmum inhibitory concentration - BSA bovine serum albumin     

Cell wall assembly in vitro from Chlamydomonas reinhardi

Summary The conditions for in vitro dissociation and reassembly of the cell wall of Chlamydomonas reinhardi have been investigated. The cell wall dissociates in aqueous 8 M lithium chloride to two homogeneous components (6.8 S₂₀w and 9.3 S₂₀w)and dialysis of the cell wall subunits against water causes reassembly of a product having the same overall morphology and chemically similar to the original cell walls. Cell wall subunits in 8 M lithium chloride alone do not reassemble on dialysis against water to form cell walls but a nucleation centre has to be provided.