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Adherence of the enteric protozoan parasite Entamoeba histolytica is mediated by an N-acetyl D-galactosamine (GalNAc)-specific lectin, a heterodimer of heavy (170 kDa) and light (35/31 kDa) subunits. The gene families encoding the lectin subunits were characterized using clamped homogeneous electric field (CHEF) gel electrophoresis in the strain HM1:IMSS. The heavy subunit was shown to be encoded by a family of five hgl genes, which were physically mapped to five distinct HindIII restriction fragments. The light subunit was shown to be encoded by a family of lgl genes located at six loci in the genome. Heavy and light subunit genes did not appear to be linked. Partial sequences of new members of the hgl and lgl gene families were obtained. Several different strains of E. histolytica were found to contain multiple hgl loci in their genomes. Expression of hgl and lgl genes in HM1:IMSS trophozoites was examined under different growth conditions using the reverse transcription-polymerase chain reaction (RT-PCR). mRNA transcripts were detected from three hgl genes and three lgl genes, with no significant differences between cultured amoebae and amoebae from liver abscesses. The complexity of GalNAc lectin gene expression observed suggests distinct biological functions for the products of the individual genes during pathogenesis.

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Fig. 1), the 3' portion of the luciferase gene from pGEM-luc was amplified by using the polymerase chain reaction (PCR) with the primers 94 and 95 (all nucleotides used for plasmid construction are described in Table 1), which added a syntheticXho I site in the amplified product two bases 3' of the stop codon of luciferase. The amplified product and pGEM-luc were digested with Cla I and Xho I and were ligated together with T4 DNA ligase (GIBCO/BRL). By effectively deleting 53 bases between the stop codon of the luciferase gene and the Xho I site in the multicloting site ofpGEM-luc, 3' amebic sequences could be ligated in close proximity to the 3' terminus of the reporter gene. A short 3' untranslated region in amebic mRNA is typical and may prove critical to message stability.To make the AA2R8 construct, approximately 1 kb of the 5' flanking region of hgll was PCR-amplified from a genomic clone containing the 5' coding region and flanking region of hgll (6) Abbreviations: E-64, trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane; E-64c, (2S,3S)-trans-epoxysuccinyl-L-leucylamido-3-methylbutane; SV40, simian virus 40. *To whom reprint requests should be addressed. 7099The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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