Cyelic Monophosphate-Dependent Adenosine Triphosphate
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Proc. Nat, Acad. Sci. USA Vol. 70, No. 4, pp. 1254-1257, April 1973 A 5'-Adenosine Monophosphate-Dependent Adenylate Cyclase and an Adenosine 3': 5'-Cyelic Monophosphate-Dependent Adenosine Triphosphate Pyrophosphohydrolase in Dictyostelium discoideum (chemotaxis/enzyme regulation/phosphodiesterase/5'-nucleotidase/Polysphondylium violaceum) EDWARD F. ROSSOMANDO* AND MAURICE SUSSMAN Department of Biology, Brandeis University, Waltham, Massachusetts 02154 Communicated by William P. Jencks, February 6, 1973 ABSTRACT Cell aggregation in Dictyostelium dis- MATERIALS AND METHODS coideum appears to involve the production and detection of 3': 5'-cyclic AMP. Two pertinent catalytic activities have OrganiSms. Nwo strains of D. discoideum were used. Ax-3 been studied in concentrates from D. discoideum purified is derived from the parent stock, NC-4, and is adapted for 50- to 100-fold. They are (i) adenylate cyclase and (ii) growth in axenic medium (10). R-46 is a mutant with altered ATP pyrophosphohydrolase. ATP pyrophosphohydrolase activity converts ATP to 5'-AMP and pyrophosphate. The aggregative performance and very low phosphodiesterase presence of 5'-AMP is an absolute requirement for adeny- activity (less than 1% of that of the wild type). The third late cyclase activity. The presence of 3':5'-cyclic AMP is organism is a related species, Plysphondylium violaum. an absolute requirement for ATP pyrophosphohydrolase activity. Both activations, particularly that of ATP pyro- Enzyme Purifwation. Cells were grown and harvested as phosphohydrolase, show narrow ranges of specificity and described (7) and stored in frozen pellets. After they were display significant cooperativities. thawed, the pellets were suspended in buffer VI [20 mM After growth, the cells of Dictyostelium discoideum migrate in Tris * HCI-50 mM NaCl (pH 7.4)], treated in a Branson sonifier directed fashion toward central collecting points, enter onto (1 min at 2 amp), and centrifuged at 30,000 X g for 30 min. organized multicellular aggregates, and construct fruiting The supernatant was centrifuged at 100,000 X g for 3 hr. bodies. This directed movement is the result of a chemotactic Solid ammonium sulfate was added to the supernatant frac- attraction exerted upon outlying individual cells by the tion to obtain the protein that precipitated between 40 and nascent aggregative center and its radiating cell streams 65% saturation. This material was dissolved in and dialyzed (1, 2), and appears to involve the production and detection against buffer VI for 4 hr, then applied to an agarose (6% of 3': 5'-cyclic adenosine monophosphate (cAMP) (3). Bio-gel A5) column (11) and eluted with the same buffer. In order to understand the biochemical basis of this chemo- The effluent was monitored with a flow cell and recorder tactic response, attempts have been made to identify and (LKB) at 280 nm and collected. 'H20 was added to the characterize some of the macromolecular elements that might applied sample for measurement of the included volme.'All be involved. Thus, two 3': 5'-cAMP phosphodiesterase ac- operations were done at 4°. 6+! 7 tivities have been reported, the first with a molecular weight Enzyme Assays. The cyclase and pyrophosphohydrolase of about 132,000 and a Km of 2 mM (4) and a second with a were measured by following the- conversion of ['H]ATP to molecular weight of about 65,000 and a Km of 15MuM (4-6). either cAMP or 5'-AMP. After incubation at 370, the com- In our previous communication we reported the presence ponents of the reaction mixture were separated by thin-layer of an adenylate cyclase activity in crude extracts of D. di"- chromatography as described (7). This procedure separates coideum and a cAMP-dependent ATPase (7). We have since ATP, 5'-AMP, cAMP, and adenosine. The reaction mixture characterized the products of the latter reaction as adenosine contained, in a final volume of 100 jsl:2 JAmol of Tris HCl 5'-monophosphate (5'-AMP) and pyrophosphate (PPi). (pH 7.4), 17 nmol of [$H]ATP (2 X 104 cpm/nmol), 10.umol Hydrolases of this type have been reported in bull seminal of NaF, and various amounts of either 5'-AMP or cAMP. fluid (8) and snake venom (9), and were termed "PP-forming The cAMP phosphodiesterase was assayed by following the ATPase" and "a,#-ATPase." The designation, ATP pyro- conversion of ['H]3':5'-cAMP to 5'-AMP. 5'-Nucleotidase phosphohydrolase, would seem to be more appropriate, and activity was determined by measurement of the conversion we use it hereafter. of ['H]5'-AMP to adenosine. Under these conditions, the The experiments we shall describe, using a partially purified initial reaction rates were directly proportional to enzyme (50- to 100-fold) preparation of the cyclase and pyrophos- concentration. phatase, indicate that both enzymes have interesting regula- tory properties that raise the possibility that they may func- Demonstration of ATP Pyrophosphohydrolase. The use of a tion in vivo in a regulatory loop during the aggregation process. substrate mixture containing ['HJATP and ["2P]ATP labeled only in the gamma position demonstrated that 5'-AMP and PPi are produced in equimolar quantities. Addition of excess * Present Address: Department of Oral Biology, University of unlabeled ADP was without effect. The concentrations of un- Connecticut Health Center, Farmington, Conn. 06032. labeled cAMP necessary to activate the enzyme were also 1254 Proc. Nat. Acad. Sci. USA 70 (1978) Enzyme Regulation in Slime Mold 1255 C.)1= MOLECULAR WEIGHT X10-5 0 w CO) -J 0 cc Fn .0I CO) I M 0 C,)e I0)m 0 0 010 I-q> z VOLUME (ml) w Co C, C, FIG. 1. Chromatography of a preparation of strain Ax-3 on a 2 X 170 cm column of 6% agarose. About 85 mg of protein was applied in 3 ml to the column. The column was eluted at 13 ml/hr, and absorbance was measured continuously in the effluent. Phosphodiesterase, ATP pyrophosphohydrolase, and adenylate cyclase activities were measured in the effluent fractions and recorded in arbitrary units. Arrow indicates included volume. sufficient to rule out the possibility that the labeled 5'-AMP phodiesterase activity wasnotdetecta~ble in these concen- was coming from cAMP. Furthermore, no cAMP phosphodi- -tratls.- Thei 5-nucleotidase activity, though present, was esterase activity could be detected (in the purified fraction completely inhibited by the presence of fluoride (12). Con- used) nor any nonspecific phosphatase activity (with p- sequently, the cyclase and pyrophosphohydrolase activities nitrophenylphosphate as substrate). could be assayed unequivocally by measurement of the ac- cumulations of the respective reaction products, cAMP and Materials. ['H]ATP (13.4 Ci/mmol), ['H]3': 5'-cAMP (21 5'-AMP. Ci/mmol), and ['H]5'-AMP (12.6 Ci/mmol) were obtained from New England Nuclear Corp. All unlabeled nucleotides and nucleosides were from Sigma; cellulose chromatographic 5'-AMP Dependence of the Adenylate Cyclase. Preliminary sheets were from Eastman Kodak. All other chemicals and purifications of the cyclase indicated a requirement for an solvents were reagent grade or better. Agarose was from Bio activator of small molecular weight that could be met by addi- Rad Laboratories. Proteins were determined by the Lowry tion of 5'-AMP to the reaction mixture. The kinetics of cAMP et al. procedure, with bovine-serum albumin as standard (13). production in the presence of different concentrations of 5'- AMP are shown in Fig. 2A. The rates were constant for about RESULTS 20 min and then diminished progressively, though never com- Removal of Phosphodiemterase Activity. Fig. 1 shows the pro- pletely during the next 20 min. Several trivial explanations of file of material absorbing at 280 nm and the distribution of this diminution have been eliminated. Thus, it is not due to enzyme activities in the agarose column effluent (see Methods). disappearance of the activator, 5'-AMP, or the product, The adenylate cyclase and ATP pyrophosphohydrolase activi- cAMP, since either compound, suitably labeled and added to ties were eluted together in an effluent volume that would the reaction mixture, could be quantitatively recovered after correspond to a globular protein of 100,000 A 10,000 daltons. 40 min of incubation. The recovery of added 5'-AMP also By this criterion the cyclase appears similar to the cyclase of ruled out the possibility that it contributes stoichiometrically Escherichia coli (14). The intracellular phosphodiesterase ac- to the reaction. (Moreover, separate experiments failed to re- tivity was eluted in two separate fractions. One appeared at veal the presence of adenylate kinase activity in these frac- an effluent volume that would correspond to a globular protein tions.) The enzyme itself is not unstable at 370, since prior of 60,000 daltons, similar to the enzyme reported by Gerisch incubation even at 450 for 10 min did not reduce its activity and coworkers (5) and Chassy (4). detectably. Addition of fresh substrate or complete reaction The fractions containing the maximum cyclase and pyro- mixture after 20 min did not accelerate the reaction. phosphohydrolase activities were pooled and concentrated by In Fig. 3A the initial rates of cAMP production are plotted positive pressure filtration (Amicon Ultrafiltration Mem- as a function of 5'-AMP concentration. The relationship brane). T Vi tions showed about 50- to 100-fold increases shows a significant degree of cooperativity. Purified adenylate in specific activity o sonites. Phos- cyclase from mutant R46 of D. discoideum and from another 1256 Cell Biology: Rossomando and Sussman Proc. Nat. Acad. Sci. USA 70 (1973) TABLE 1. Effect ofpurine nucleotides on adenylate cyclase activity Concentration Concentration Nucleotide (mM) (nmol/30 min) 5'-AMP 1.9 1.10 0.8 0.50 5'-GMP 1.7 0.34 0.85 0.15 2'- and 3'-AMP 1.8 0 0.9 0 ADP 1.5 0 0.75 0 5'-dAMP 2.10 0.90 1.05 0.50 5'-IMP 1.9 0 0.8 0 Standard reaction mixtures containing the nucleotides at the specified (final) concentrations were incubated with 35 /.tg of enzyme protein present at 370 for 30 min.