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			PubMed Journals: Proc Natl Acad Sci U S A

  Source:		PMID: 146197


    		Proc Natl Acad Sci U S A. 1977 Dec;74(12):5377-81.
     
			Chemical evidence that proteolytic cleavage
			causes the heterogeneity present in human
			ceruloplasmin preparations.

			Kingston IB, Kingston BL, Putnam FW.

			Nine samples of human ceruloplasmin [iron(II):oxygen
			oxidoreductase; EC 1.16.3.1] prepared by
			different procedures have been examined
			for heterogeneity; gel electrophoresis showed
			that seven contained a number of components
			with molecular weights ranging from 20,000
			to 130,000, and two contained largely a
			single component of molecular weight 130,000.
			Digestion of a single-component preparation
			with plasmin produced fragments with molecular
			weights similar to those found in the multicomponent
			preparations. Amino-terminal analysis, peptide
			mapping, and amino acid analysis showed
			that plasmin digestion generated a fragment
			of 20,000 molecular weight, which corresponded
			to a component present in a multicomponent
			ceruloplasmin preparation. The 20,000 molecular
			weight fragment appears to correspond to
			the so-called alpha-subunit or L-chain of
			human ceruloplasmin. Chemical evidence is
			thus provided that ceruloplasmin is a single-chain
			protein and that the so-called subunits
			are fragments. The 20,000 molecular weight
			fragment contains a single cysteine; amino
			acid sequence studies have shown that the
			sequence in the vicinity of this residue
			is similar to that around the single cysteine
			residue in plant plastocyanins and bacterial
			azurins, which are small, blue, copper-containing
			proteins.

			PMCID: PMC431726 PMID: 146197 [Indexed
			for MEDLINE]

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