HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Conroy, M. C. Articles by Lepow, I. H. Search for Related Content PubMed Articles by Conroy, M. C. Articles by Lepow, I. H.

Structural Features and Biologic Properties of Fragments Obtained by Limited Proteolysis of C3¹

From the Departments of Pathology, Biochemistry, and Medicine, Health Center, University of Connecticut, Farmington, Connecticut 06032

Abstract

Limited proteolysis of the third component of human complement (C3) was performed by using trypsin and streptococcal proteinase and the digests were analyzed for biologic activity. Incubation of C3 with trypsin for 1 min yielded a peptide with smooth muscle-contracting activity but no chemotactic activity, whereas the digest obtained after 15 min of incubation had only chemotactic activity. The conversion of muscle contracting to chemotactic activity could be correlated with the time course of trypsin hydrolysis. Hydrolysis of C3 with streptococcal proteinase gave a digest demonstrating only chemotactic activity. Each digest was resolved on a Sephadex G-100 column and the fractions containing biologic activities were characterized. The amino acid composition of the trypsin fragments, despite having different biologic activities, was remarkably similar, although differences in NH₂-terminal amino acids were demonstrable. The fragments obtained by digestion of C3 with the streptococcal proteinase had an amino acid composition different from the trypsin fragments and displayed marked heterogeneity of NH₂-terminal residues. These results suggest that slight alterations in the primary structure of C3 fragments may yield significant changes in their biologic activities and that the structural requirements for chemotactic activity are not confined to a single peptide species.

Footnotes

¹ This work was supported by Grants AI-08251, National Institute of Allergy and Infectious Diseases, United States Public Health Service and GM-20520, National Institutes of Health. It was presented in part at the American Academy of Allergy, Miami, Florida, January 1974 (J. Allergy 53: 77, 1974).

² Predoctoral Fellow in Immunology, Training Grant AI-00438, National Institute of Allergy and Infectious Diseases. United States Public Health Service; taken in part from a thesis submitted to the Graduate School of the University of Connecticut in partial fulfillment of requirements for the Ph.D. degree. Present address, Johns Hopkins School of Medicine at Good Samaritan Hospital, Baltimore, Maryland 21239.