A microdomain for protein secretion in Gram-positive bacteria

Gram-positive bacteria face unique challenges in generating biologically active conformations for their exported proteins because they lack a dedicated compartment for folding secreted polypeptides. We have discovered that protein secretion by way of the general secretory (Sec) pathway in the important human pathogen Streptococcus pyogenes proceeds through a single microdomain. Unlike other mechanisms for asymmetry involving the Sec pathway, proteins destined for secretion are targeted to a single locus distal to either cell pole that has specialized to contain the Sec translocons. This subcellular organization may represent a paradigm for secretion common to other Gram-positive pathogens with profound implications for pathogenesis.     

Interleukin-2 induction of T-cell G1 progression and c-myb expression

In studies to determine the biochemical mechanisms responsible for cell proliferation, synchronized T cells were used as a model for cellular growth control. By metabolic and morphologic criteria, it was found that activation of the T-cell antigen receptor rendered the cells responsive to interleukin-2 (IL-2), but did not move them through the cell cycle. Instead, IL-2 stimulated G1 progression to S phase, or lymphocyte "blastic transformation." During IL-2-promoted G1 progression, expression of the cellular proto-oncogene c-myb was induced transiently at six to seven times basal levels, maximal levels occurring at the midpoint of G1.     

A dearth of dark matter in ordinary elliptical galaxies

The kinematics of the outer parts of three intermediate-luminosity elliptical galaxies were studied with the Planetary Nebula Spectrograph. The galaxies' velocity-dispersion profiles were found to decline with the radius, and dynamical modeling of the data indicates the presence of little if any dark matter in these galaxies' halos. This unexpected result conflicts with findings in other galaxy types and poses a challenge to current galaxy formation theories.