So I'm doing a research project for my school and I'm trying to decide on the exact nature of the project. My current plan is to try to genetically engineer E. coli or Yeast to produce spider silk protiens. However when trying to find an appropriate gene for my project I learned that the common house spider's silk has two different spidroin protiens. Just by a simple google search I can't tell the difference. So, what is the difference between spidroin-1 and spidroin-2
I've looked into literature on this. Wow, there is a lot of research on this. Here's a quick summary:
Functionally they are very similar. Both are fibrous proteins. Together they constitute spider silk. Sp-1 and Sp-2 are two different genes, often present in multiple copies in the genome, depending on which spider species you consider. They differ in amino acid content and are post-translationally modified differently. Sp-2, for instance, is heavily modified. There also exist different transcriptional isoforms of these proteins. It seems quite complex.
There are also different types of silk. You may be referring to major ampullate silk, which is only one of six different types of silk fibres spun by the spiders of the genus Nephila. Only this one contains major ampullate spidroin-1 (MaSp1) and major ampullate spidroin-2 (MaSp2).
Excerpt from one paper on the subject, which lists some differences:
MaSp1 and MaSp2 are large proteins of about 250 to 350 kDa that share a general domain architecture. Both proteins contain a large, central, repetitive domain that consists of approximately 100 tandem copies of a 30 to 40 amino acid repeat sequence. The consensus repeat sequences for both MaSp1 and MaSp2 are glycine-rich and end in poly-alanine motifs (usually four to seven residues long). For MaSp1, the consensus repeat includes (GGX)n motifs (where X = A, L, Q, or Y) and very low proline content. In contrast, the MaSp2 consensus repeat has significant proline content and characteristic motifs such as GPG and QQ. The repetitive domains of different spidroins display a relatively high level of amino acid sequence variation that has been implicated in providing the elasticity and toughness that is characteristic of the different fibers.
It is possible that different amounts of Sp-1 and Sp-2 are combined to tune the elasticity and toughness of the silk. I have no idea whether the mechanical properties of silk are changed by the spider to suit the context (e.g. elasticity in windy conditions, or whether the content changes seasonally in response to temperature differences). That would make for a cool research hypothesis.