Ultramarine fluorescent protein, construction method therefor and use thereof in preparation of protein sunscreen agent

A method for constructing an ultramarine fluorescent protein comprising:

• 1) obtaining DNA molecules by using PCR site-directed mutagenesis:
• carrying out PCR site-directed mutagenesis by using mutation primers based on F46L, T65Q, W66F, Q69L, Y145G, H148S and T203V sites, with pETCFP-Cl as a template;
• 2) transforming the obtained DNA molecules into E. coli DH5α, and obtaining the gene-mutated UFP after bacteria selection and sequencing;
• 3) double enzyme digesting pETUFP-Cl, and expression vectors pET-24a and pHND by restriction enzymes BamH I/EcoR I, respectively, and then ligating to construct a pET-24a-UFP vector and a pHND-UFP expression vector for UFP expression;
• 4) transforming a mutated plasmid into BL21(DE3), inoculating bacteria culture which has been cultured overnight in a liquid medium, and collecting the bacteria pellets;
• 5) taking a lysis buffer, suspending the bacteria pellet in the lysis buffer, breaking the bacteria by ultrasonication in an ice bath after suspended well, performing centrifugation and collecting a supernatant;
• 6) heating the supernatant, extracting with an organic solvent, and then dialyzing the supernatant to remove impurities, concentrating the protein by low-speed centrifugation in a 3 kD ultrafiltration tube, determining concentration of the UFP according to a Bradford method.