Volume 17, Issue 5 p. 465-474

Identification and characterization of multiple Spidroin 1 genes encoding major ampullate silk proteins in Nephila clavipes

W. A. Gaines IV

W. A. Gaines IV

Department of Genetics and Biochemistry and

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W. R. Marcotte Jr

W. R. Marcotte Jr

Department of Genetics and Biochemistry and

Department of Biological Sciences, Clemson University, Clemson, SC, USA

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First published: 16 September 2008
Citations: 39
William R. Marcotte, Jr, Department of Genetics and Biochemistry, 51 New Cherry Street, Biosystems Research Complex, Room 216, Clemson University, Clemson, SC 29634, USA. Tel.: +1 864 656 0119; fax: +1 864 656 0119; e-mail: [email protected]

Abstract

Spider dragline silk is primarily composed of proteins called major ampullate spidroins (MaSps) that consist of a large repeat array flanked by nonrepetitive N- and C-terminal domains. Until recently, there has been little evidence for more than one gene encoding each of the two major spidroin silk proteins, MaSp1 and MaSp2. Here, we report the deduced N-terminal domain sequences for two distinct MaSp1 genes from Nephila clavipes (MaSp1A and MaSp1B) and for MaSp2. All three MaSp genes are co-expressed in the major ampullate gland. A search of the GenBank database also revealed two distinct MaSp1 C-terminal domain sequences. Sequencing confirmed that both MaSp1 genes are present in all seven Nephila clavipes spiders examined. The presence of nucleotide polymorphisms in these genes confirmed that MaSp1A and MaSp1B are distinct genetic loci and not merely alleles of the same gene. We experimentally determined the transcription start sites for all three MaSp genes and established preliminary pairing between the two MaSp1 N- and C-terminal domains. Phylogenetic analysis of these new sequences and other published MaSp N- and C-terminal domain sequences illustrated that duplications of MaSp genes may be widespread among spider species.