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The amino acid sequence of all but a few N-terminal residues of the beta subunit of rat liver ATP synthase has been determined from cDNA clones. Rat liver F1-beta is shown to contain 17 amino acid differences from that reported for F1-beta of bovine heart, 2 differences of which involve differences in charge. This may account in part for the observation that bovine heart F1 binds nucleotides with much greater affinity than the rat liver enzyme. Rat liver F1-beta also contains homologous regions with another nucleotide binding protein, adenylate kinase, for which high-resolution structural studies are available. Adjacent to one of these homologous regions is an eight amino acid stretch which bears striking homology to the phosphorylation region of the (Na+,K+)-ATPase. The combination of these two homology regions may constitute at least part of a nucleotide binding domain in F1-beta. Significantly, both rat liver and bovine heart beta contain these regions of homology, whereas the 17 amino acid differences between the two enzymes lie outside this region. The possibility of a second nucleotide binding domain which differs between the two enzymes is discussed. A cDNA clone containing all the regions of homology as well as 11 of the 17 amino acid differences between the bovine heart and rat liver beta subunits has been ligated into the bacterial expression vector pKK223-3. After transformation of a protease-deficient strain of Escherichia coli, this cDNA clone is expressed as a 36-kilodalton protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Despite rapid advances in imaging technology, the etiology of stroke remains unestablished in 40% of patients. MRI improves localization in acute stroke. However, it is not known whether "accurate localization" results in better management. We reviewed the hospital records of all patients admitted with a diagnosis of acute ischemic stroke and who had had cranial CTs and MRI within 10 days of admission. Between January 1987 and June 1990, 116 patients (69 men, 47 women; mean age, 66 years) were identified. Compared with CT localization, infarcts were better localized in nine of 39 patients with cerebral cortical lesions, in 20 of 22 patients with brainstem and cerebellar lesions, and in three of three patients with isolated cerebellar lesions. In 22 patients (18.9%), MRI showed multiple infarcts in two or more vascular territories, suggesting embolic disease and leading to anticoagulation. MRI also showed arterial occlusions in 11 patients (9.5%). Based on the information obtained with MRI, the clinical diagnosis was changed in 19 patients (16.3%), resulting in changes in the management of most of those patients. Thus, we confirm earlier reports that MRI improves localization after acute cerebral infarction and show that such information alters patient management.

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