title: Molecular properties of elongation factor Tu from Streptomyces aureofaciens and Escherichia coli.
abstract: Some molecular properties of the elongation factor Tu of protein synthesis purified in an aggregated state from gram-positive Streptomyces aureofaciens were studied and compared with those of Tu from gram-negative Escherichia coli. Electrofocussing under reducing conditions showed that the molecule of EF-Tu from S. aureofaciens has an isoelectric point shifted more to the acidic side compared with EF-Tu from E. coli. A comparison of amino acid composition revealed minor differences in the content of several amino acids in the two factors and showed that EF-Tu from S. aureofaciens contains four half-cystines per molecule. Under denaturing conditions only two mercapto groups reacted with 5,5'-dithiobis(2-nitrobenzoic acid). Limited tryptic digestion of aggregated EF-Tu from S. aureofaciens yields six fragments: the four main fragments are of a similar size as those of the E. coli factor. All fragments detected after trypsin digestion of S. aureofaciens EF-Tu were immunologically cross-reactive with antibodies against E. coli EF-Tu. However, even after 2 h of the reaction there still remains a small part of streptomycete factor uncleaved, which documents high resistance of aggregated EF-Tu towards trypsin.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D004586:Electrophoresis; D004926:Escherichia coli / Q000032:analysis*; D006868:Hydrolysis; D007525:Isoelectric Focusing; D010444:Peptide Elongation Factor Tu / Q000302:isolation & purification*; D013304:Streptomyces aureofaciens / Q000032:analysis*; D013329:Structure-Activity Relationship; D013438:Sulfhydryl Compounds; D014357:Trypsin
chemical_list: D000596:Amino Acids; D013438:Sulfhydryl Compounds; D014357:Trypsin; D010444:Peptide Elongation Factor Tu