Dispensable pieces of an aminoacyl tRNA synthetase which activate the catalytic site.

Recent data suggest that size polymorphism of aminoacyl tRNA synthetase is due to variable fusions of additional functional domains to a catalytic core so that, in a large synthetase, a substantial part of the polypeptide is dispensable for catalytic activity. We demonstrate here that a dispensable domain, joined to the catalytic core of a large synthetase, can activate the catalytic sites. This is shown by complementation of an activity-deficient mutant enzyme by protein fragments that contain internal deletions within the catalytic domain and are themselves devoid of activity.

Modular arrangement of functional domains along the sequence of an aminoacyl tRNA synthetase.

Gene deletions show that much of Escherichia coli alanine tRNA synthetase is dispensable for each of three activities and that these activities appear to require specific domains arranged linearly along the polypeptide. Thus, variable fusions of extra polypeptide domains to a catalytic core may account for the diverse of aminoacyl tRNA synthetases.

Cycloheximide resistance in yeast: the gene and its protein.

Mutations in the yeast gene CYH2 can lead to resistance to cycloheximide, an inhibitor of eukaryotic protein synthesis. The gene product of CYH2 is ribosomal protein L29, a component of the 60S ribosomal subunit. We have cloned the wild-type and resistance alleles of CYH2 and determined their nucleotide sequence.

The radiographic evaluation of infants with stridor.

In the elective evaluation of infant stridor, inspiratory plain radiographs of the neck and chest are routinely obtained with fluoroscopy and a barium swallow when indicated. Several factors, including patient positioning, roentgenographic technique, and the phase of respiration, may significantly alter the appearance of the airway, reducing the diagnostic accuracy of this modality and leading to misinterpretation of the pathologic changes.