The intracellular location of methane mono-oxygenase (MMO) (soluble or particulate) in Methylosinus trichosporium OB3b is dependent on the availability of copper in the growth medium. Raising the Cuz+ concentration from 1 VM to 5 p~ effected a transition from soluble to particulate MMO activity, and changes in major cell polypeptides were observed on SDSpolyacrylamide gels. Organisms containing soluble MMO oxidized a wide range of substrates including n-alkanes, n-alkenes, aromatic and alicyclic compounds. By contrast, organisms containing particulate MMO did not oxidize aromatic or alicyclic compounds. These observations provide further evidence that the two types of MMO are fundamentally different.

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Branched stem bearing leaves and cone 87 impossible to draw any decisive conclusions as to the 70 STUDIES IN FOSSIL BOTANY morphology or affinities of Cingularia. We cannot be absolutely certain of the accuracy of our interpretations, and still less can we be certain whether we have to do with a Calamarian or a Sphenophyllaceous plant.These questions can only be cleared up if specimens with the structure preserved should be discovered. 5. Archaeocalamites.-A fourth type of Calamarian fructification remains to be noticed.This is a simple one to describe, because it has much in common with that of the only surviving genus of Equisetales, the recent Equisetum.The remarkable genus Archaeocalamites, characteristic of the oldest Carboniferous 'strata and of the Upper Devonian, appears, according to M. Renault's observations, to have borne the fructification of which a fragment is represented in Fig.

The distribution of methane mono-oxygenase (MMO) activities between particulate and soluble fractions of cell-free extracts of Methylosinus trichosporium OB3 b was dependent upon growth conditions. Particulate activity was associated with the presence of intracytoplasmic membranes observed only under oxygen-limiting conditions in shake flask cultures. Particulate and soluble activities showed substantially different sensitivities to a range of potential inhibitors. The particulate enzyme was inhibited by metal-chelating agents, thiol reagents and amytal, whereas the soluble MMO was not inhibited by these compounds; both activities were sensitive to KCN, ethyne and 8-hydroxyquinoline. NAD(P)H was the only suitable electron donor. The activities were unstable at 0 OC but the soluble enzyme could be partially stabilized by several compounds. The particulate and soluble MMO activities are compared with previously reported particulate and soluble MMO enzymes from this species and other methane oxidizers.

The X-ray crystal structure of 7,8-dihydro-6-hydroxymethylpterinpyrophosphokinase (PPPK) in a ternary complex with ATP and a pterin analogue has been solved to 2.0 A î resolution, giving, for the first time, detailed information of the PPPK/ATP intermolecular interactions and the accompanying conformational change. The first 100 residues of the 158 residue peptide contain a L LK KL LL LK KL L motif present in several other proteins including nucleoside diphosphate kinase. Comparative sequence examination of a wide range of prokaryotic and lower eukaryotic species confirms the conservation of the PPPK active site, indicating the value of this de novo folate biosynthesis pathway enzyme as a potential target for the development of novel broad-spectrum anti-infective agents.z 1999 Federation of European Biochemical Societies.