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|Title:||Interaction of the I Colicins With the Outer Membrane of Escherichia Coli: I. Purification and Characterization of the Colicin I Receptor. Ii. Proteolytic Activity Associated With the Outer Membrane|
|Author(s):||Bowles, Linda Kay|
|Department / Program:||Microbiology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The receptor for the I colicins is an outer membrane protein. The purified receptor consists of a single, acidic (pI = 4.75) polypeptide whose apparent molecule weight on sodium dodecyl sulfate polyacrylamide gels is 45,000 or 74,000 daltons, depending on the treatment of the protein prior to electrophoresis. Formation of a stable complex of colicin Ia with the purified protein can be demonstrated by several techniques. Analysis of the outer membranes of sensitive and resistant strains confirms the conclusion that this purified protein is the in vivo receptor.
The I colicins can be cleaved by isolated outer membranes. This cleavage is not mediated directly by the colicin receptor and is not dependent on the presence of the receptor, nor on interaction with the receptor. Cleavage of the colicin I molecule can be extensive or limited, depending on the conditions of incubation. The degradation of the colicin molecule is inhibited by diisopropyl fluorophosphate (DFP), p-nitrophenyl-p-guanidinobenzoate (NPGB), aprotinin, and N-(alpha)-p-tosyl-L-lysine chloromethyl ketone, but not N-ethylmaleimide, ethylenediamine tetraacetic acid (EDTA), or B-mercaptoethanol. The proteolytic activity of the outer membrane can be solubilized by Triton X-100 and EDTA.
Isolated outer membranes can also specifically activate plasminogen to plasmin with a Km(,(app)) of 31.5 (mu)M. This proteolytic activation is inhibited by DFP, NPGB, and aprotinin.
Intact Escherichia coli can cleave colicin at 45(DEGREES) and 50(DEGREES)C, but not 37(DEGREES)C. E. coli cells appear to activate plasminogen at temperatures above 40(DEGREES)C.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-16|