Asymmetric Aggregation Research Articles

Fruiting body morphogenesis in submerged cultures of Myxococcus xanthus.

Induced by starvation, the development of fruiting bodies by Myxococcus xanthus on glass and plastic surfaces under a layer of liquid was followed microscopically. Calcium ions and a neutral pH were required for development of a Myxococcus strain that grew dispersed in liquid culture. Initially asymmetric aggregates later became round, and sporulation followed aggregation.

Constitutive Inorganic Pyrophosphatase of Escherichia coli: V. RECONSTITUTION OF NATIVE ENZYME PARTICLES FROM SUBUNIT POLYPEPTIDE CHAINS

Abstract In concentrated guanidine hydrochloride solutions Escherichia coli pyrophosphatase dissociated to 6 randomly coiled polypeptide chains of molecular weight 20,000. When the guanidine salt was removed by dialysis, enzymatic activity reappeared, provided that a sulfhydryl compound was present during the renaturation process. The reconstituted enzyme had a molecular weight and sedimentation-diffusion properties which were indistinguishable from those of native protein. Optical, electrophoretic, and catalytic properties of reconstituted and native enzymes were also identical. If the protein cysteine groups (2 per polypeptide subunit) were allowed to form disulfide bonds, inactive, compact globular structures, about half the size of native protein, were formed upon removal of guanidine hydrochloride. Alkylation of the cysteines with N-ethylmaleimide and subsequent removal of the guanidine salt also yielded an inactive preparation; this appeared to consist of large, asymmetric aggregates of partially unfolded chains.

Étude par electrophorèse et ultracentrifugation de la composition protéinique de la couche musculaire des carotides de bovidé

Resume It is now generally admitted that smooth muscle and striated muscle show similar proteinic composition. But physiological researches carried out principally on cow carotis led us to the conclusion that this tissue contains, in addition to the normal contractile system, another contractile system which controls the muscular tonus. The present paper describes our research on the composition of proteins of the muscular layer in the carotis of cow by means of free boundary electrophoresis and ultracentrifugation. As compared to striated muscle there are marked differences in protein composition, not only regarding the myogen but also the structure proteins. It is possible to extract from the carotis muscle a structure protein soluble at low ionic strength in presence of traces of ATP. Its behaviour when ultracentrifugated at an ionic strength of 0.35 and with 0.5% ATP clearly indicates that it results from an association of two proteins. For that reason, we named it tonoactomyosin. This protein is probably dissolved in the sarcoplasm in the form of highly asymmetric aggregates, the degree of dissociation depending on the ATP concentration. The increase in the K + content of the mascular cell, which produces an increase of tonus, is likely to favorize the interaction of these aggregates, yielding a more rigid network connected with syneresis.