No abstract

B exhibited areas at which cell wall and protoplasmic membrane were intimately associated. These areas became visible in ultrathin sections after the bacteria had been fixed and embedded in plasmolysed state. At numerous areas the protoplasmic membrane was observed to adhere to the wall, while the protoplast had shrunk. Duct-like extensions of the protoplasmic membrane were thus formed. Two hundred to 400 of these wall membrane associations are found per bacterium of E. coli B . In a number of cells the chromosomal material is seen in close proximity or connected to a wall membrane association.

The recessive mutation at the pale ear (ep) locus on mouse chromosome 19 was found to be the homologue of human Hermansky-Pudlak syndrome (HPS). A positional cloning strategy using yeast artificial chromosomes spanning the HPS locus was used to identify the HPS gene and its murine counterpart. These genes and their predicted proteins are highly conserved at the nucleotide and amino acid levels. Sequence analysis of the mutant ep gene revealed the insertion of an intracisternal A particle element in a protein-coding 3 exon. Here we demonstrate that mice with the ep mutation exhibit abnormalities similar to human HPS patients in melanosomes and platelet-dense granules. These results establish an animal model of HPS and will facilitate biochemical and molecular analyses of the functions of this protein in the membranes of specialized intracellular organelles.