BRUGIA SPP AND LITOMOSOIDES-CARINII - IDENTIFICATION OF A COVALENTLY CROSS-LINKED MICROFILARIAL SHEATH MATRIX PROTEIN (SHP2)

A microfilarial sheath protein gene (shp2) coding for the major consti tuent of the insoluble, cross-linked sheath remnant (SR) from Brugia m alayi, Brugia pahangi and Litomosoides carinii has been cloned and seq uenced, based on peptide partial amino-acid sequences. All three close ly related single-copy shp2 genes in the two genera carry a single int ron in identical position; shp2 mRNAs are post-transcriptionally modif ied by both cis-splicing and trans-splicing. In accordance with their extracellular destinations the encoded proteins include signal peptide sequences; molecular masses of approx. 23 kDa are hence predicted for the mature secreted polypeptides. In their structures sheath matrix p roteins shp2 may be regarded as extreme cases of a modular constitutio n, since these proteins largely consist of two different segments of m ultiple sequence repetitions, PAA and QYPQAP (or QYPQ), separated by e lements of unique sequence. Extreme insolubility and cross-linking are likely to originate from these repetitive sequences within shp2, and to constitute the basic properties of a microfilarial matrix largely c onsisting of an shp2 network.