Myosin I heavy-chain genes of Acanthamoeba castellanii: cloning of a second gene and evidence for the existence of a third isoform.
We have determined the complete sequence and structure of a second myosin I heavy-chain gene from Acanthamoeba castellanii. This gene, which we have named MIL, spans approx. 6kb, is split by 17 introns, encodes a 1147-aa polypeptide, and is transcribed in log-phase cells. The positions of six of the introns are conserved relative to a vertebrate muscle myosin gene. Similar to the previously characterized MIB heavy-chain gene, the deduced MIL heavy-chain aa sequence reveals a 125-kDa protein composed of a myosin globular head domain joined to a novel, approx. 50-kDa C-terminal domain that is rich in glycine, proline and alanine residues. There are differences, however, between MIL and MIB in the sequence organization of their unconventional C-terminal domains. We conclude from this and other data that Acanthamoeba express at least three myosin I heavy-chain isoforms: MIL, plus MIA and MIB, whose purifications have been published previously. Amoeba genomic DNA blots probed with a short, highly conserved sequence whose position is transposed between MIB and MIL indicate that the Acanthamoeba myosin I heavy-chain gene family may actually contain as many as six genes. Finally, we compared the myosin I sequences with those of two related proteins, Drosophila NinaC and the bovine myosin I-like protein, and found that a portion of the unconventional C-terminal domains of the amoeba myosins I and the bovine protein appear to be related.
Jung
G
G
Laboratory of Cell Biology, NHLBI, Bethesda, MD 20892.
Schmidt
C J
CJ
Hammer
J A
JA
D000048:Acanthamoeba / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics; D005796:Genes; D008969:Molecular Sequence Data; D009218:Myosins / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D009218:Myosins