http://cssb.biology.gatech.edu/skolnick/publications/pdffiles/197.pdf

From genes to protein structure and function: novel applications of computational approaches in the genomic era

Papillomavirus infections — a major cause of human cancers

http://teachline.ls.huji.ac.il/72682/Publications/Sorensen2005.pdf

Advanced genetic strategies for recombinant protein expression in Escherichia coli.

http://home.sandiego.edu/~josephprovost/Making%20the%20most%20of%20affinity%20tags.pdf

Making the most of affinity tags.

The key enzyme in coronavirus polyprotein processing is the viral main proteinase, M(pro), a protein with extremely low sequence similarity to other viral and cellular proteinases. Here, the crystal structure of the 33.1 kDa transmissible gastroenteritis (corona)virus M(pro) is reported. The structure was refined to 1.96 A resolution and revealed three dimers in the asymmetric unit. The mutual arrangement of the protomers in each of the dimers suggests that M(pro) self-processing occurs in trans. The active site, comprised of Cys144 and His41, is part of a chymotrypsin-like fold that is connected by a 16 residue loop to an extra domain featuring a novel alpha-helical fold. Molecular modelling and mutagenesis data implicate the loop in substrate binding and elucidate S1 and S2 subsites suitable to accommodate the side chains of the P1 glutamine and P2 leucine residues of M(pro) substrates. Interactions involving the N-terminus and the alpha-helical domain stabilize the loop in the orientation required for trans-cleavage activity. The study illustrates that RNA viruses have evolved unprecedented variations of the classical chymotrypsin fold.

https://www.embopress.org/doi/pdf/10.1093/emboj/cdf327

Structure of coronavirus main proteinase reveals combination of a chymotrypsin fold with an extra alpha-helical domain.

The E6 promoters of all genital human papillomaviruses have a characteristic alignment of transcription factor binding sites. Activation of the basic transcription complex at the TATA box depends upon a sequence-aberrant Sp1 site. Repression of E6 promoters is achieved by two binding sites for the viral E2 protein positioned between the Sp1 site and the TATA box. We have purified the human papillomavirus type 16 E2 protein after expression in Escherichia coli and studied its binding and repression properties with oligonucleotides representing the homologous promoter sequences. A Kd value of 3 x 10(-10) M indicated binding properties expected for a native protein. We found low cooperativity in the binding of two E2 dimers to flanking sites, both when these sites were separated by 3 nucleotides, as in the natural promoter, and when they were further apart. E2 protein, bound close to the distal Sp1 site, displaced the Sp1 factor even when the aberrant sequence was replaced by a typical Sp1 core recognition site. The high affinity of E2 protein for its binding site even led to Sp1 displacement at concentrations of E2 protein nearly 2 orders of magnitude lower than those of Sp1. Functional analyses of mutated E6 promoter sequences showed repression by this distal E2 binding site in the complete absence of binding to the proximal E2 binding site. From our findings and observations published by others, we conclude that each of the E2 binding sites in the E6 promoter of genital human papillomaviruses plays a separate role by displacing the transcription factors Sp1 and TFIID. Images

The human papillomavirus type 16 E2 transcription factor binds with low cooperativity to two flanking sites and represses the E6 promoter through displacement of Sp1 and TFIID.

In the affinity purification of recombinant fusion proteins, the rate-limiting step is usually the efficient proteolytic cleavage and removal of the affinity tail and the protease from the purified recombinant protein. We have developed a rapid, convenient and efficient method of affinity purification which can overcome this limitation. In one example of the method, the protease 3C from a picornavirus (3Cpro), which cleaves specific sequences containing a minimum of 6-7 amino acids, has been expressed as a fusion with glutathione S-transferase. The resultant recombinant 'fusion protease' cleaves fusion proteins bearing (from the amino-terminus) the same affinity tail as the fusion protease, a 3Cpro cleavage recognition site, and the recombinant protein of interest. The recombinant protein is purified in a single chromatographic step which removes both the affinity tail and the fusion protease. The advantages over existing methods include much improved specificity of proteolytic cleavage, complete removal of the protease and the affinity tail in one step, and the option of adding any desired amount of fusion protease to ensure efficient cleavage. The potential flexibility of the method is shown by the use of various affinity tails and alternative fusion proteases.

Efficient and Rapid Affinity Purification of Proteins Using Recombinant Fusion Proteases

http://www.jbc.org/content/268/34/25735.full.pdf

Human rhinovirus-14 protease 3C (3Cpro) binds specifically to the 5'-noncoding region of the viral RNA. Evidence that 3Cpro has different domains for the RNA binding and proteolytic activities.

https://www.jbc.org/content/265/13/7180.full.pdf

Site-directed mutagenesis suggests close functional relationship between a human rhinovirus 3C cysteine protease and cellular trypsin-like serine proteases.

L. E.-C. Leong

Papers

The human papillomavirus type 16 E2 transcription factor binds with low cooperativity to two flanking sites and represses the E6 promoter through displacement of Sp1 and TFIID.

Efficient and Rapid Affinity Purification of Proteins Using Recombinant Fusion Proteases

Human rhinovirus-14 protease 3C (3Cpro) binds specifically to the 5'-noncoding region of the viral RNA. Evidence that 3Cpro has different domains for the RNA binding and proteolytic activities.

Site-directed mutagenesis suggests close functional relationship between a human rhinovirus 3C cysteine protease and cellular trypsin-like serine proteases.

Sequence and structural determinants of the interaction between the 5'-noncoding region of picornavirus RNA and rhinovirus protease 3C.