LOCATION OF PROTEINASE IN CELLS OF A SPECIES OF MICROCOCCUS

Abstract

Micrococcus sp. (ATCC No. 407) grown in tryptone yeast extract broth produced proteinase active against casein. In broth containing 2.0% sodium chloride, about 90% of the proteinase was in the culture supernatant; in broth without added salt, about 66% was associated with the cells. When such cells were washed with 2% sodium chloride, about one-half the associated proteinase was released. Presumably this saline-extractable portion of the proteinase is loosely held at the ceil surface, possibly by ionic linkages. A further yield of proteinase could be obtained from saline-washed cells by treatments that ruptured the cells or altered the permeability of the cell membrane. This so-called bound proteinase became accessible to the substrate, but was not liberated into the suspending medium on lysozyme treatment of saline-washed cells. When lysozyme-treated cells were fractionated, the proteinase was found with the cytoplasmic membrane fraction. During sonic treatment of saline-washed cells, the bound. proteinase was released without appreciable disintegration of the cell envelope suggesting that it may not be an integral part of the cell membrane.