Table 1 Three kinds of recombinant pET-28a plasmids and the corresponding recombinant proteins for each expression target

SHV-1

1. pET-28a–bla_SHV-1/6230 bp

1a. (MGSSHHHHHH…RGS)^a(SHV-1)

1b. Signal peptide–detached SHV-1

2. pET-28a–bla_SHV-1/6097 bp

2a. (MA)^a(SHV-1)(LEHHHHHH)^a

2b. (Signal peptide–detached SHV-1)(LEHHHHHH)^a

3. pET-28a–bla_SHV-1/6094 bp

3. (MGSSHHHHHH…SHM)^a( Signal peptide–removed SHV-1)

TEM-1

1. pET-28a–bla_TEM-1/6230 bp

1a. (MGSSHHHHHH…RGS)^a(TEM-1)

1b. Signal peptide–detached TEM-1

2. pET-28a–bla_TEM-1/6097 bp

2a. (MA)^a(TEM-1)(LEHHHHHH)^a

2b. (Signal peptide–detached TEM-1)(LEHHHHHH)^a

3. pET-28a–bla_TEM-1/6088 bp

3. (MGSSHHHHHH…SHM)^a( Signal peptide–removed TEM-1)