CLONING AND IDENTIFICATION OF ARP1, AN ACTIN-RELATED PROTEIN FROM PNEUMOCYSTIS-CARINII

The complete Pneumocystis carinii Arpl gene has been sequenced from two cDNA clones. The gene encodes a protein 385 bp in length with an estimated size of 45,000 kD. The A + T% for the Arpl gene and a 900-bp sequence upstream of the gene were 63.7% and 70.3%, respectively. These values are consistant with A + T codon preference displayed by P. carinii and are similar to values reported for other P. carinii genes. The predicted amino acid sequence of the P. carinii Arpl protein had a similarity of 87.6% with Neurospora crassa Arpl, 82.1% similarity with vertebrate centractin, and 71.2% similarity with the Saccharomyces cerevisiae Act5p. Expression of Arpl mRNA in P., carinii was detectable via synthesis of cDNA and subsequent PCR amplification. Affinity purified antibodies against S. cerevisiae Act5p, and canine centractin recognized both the recombinantly expressed protein and a 45,000 kD protein in P. carinii nuclear extracts. The Arpl gene is the second member of the actin multigene family that has been identified in P. carinii.