Genomic fusion protein libraries

A representative set of a- and -keto esters was also tested as substrates (total 11) for each purified fusion protein (Figure 8.13b,c) [9bj. The stereoselectivities of -keto ester reductions depended both on the identity of the enzyme and the substrate stmcture, and some reductases yielded both l- and o-alcohols with high stereoselectivities. While a-keto esters were generally reduced with lower enantioselec-tivities, it was possible to identify pairs of yeast reductases that delivered both alcohol antipodes in optically pure form. These results demonstrate the power of genomic fusion protein libraries to identify appropriate biocatalysts rapidly and expedite process development. 

Probes can be antibodies, other binding proteins constructed from protein fusions, or even oligonucleotide aptamers. While completion of the Human Genome Project has enabled access to content for nuclide acid arrays, the content for protein arrays is largely based upon available antibody libraries. Thus, the commercialization of protein microarrays remains largely dependent upon both commercial and institutional providers of protein content. These providers must also permit access to the data-based protein annotations. These are necessary in order for the protein array to be useful as a bioinformatics tool. 

Although mass spectrometry has made significant strides in sensitivity and proteome coverage, a recent report by Weissman and co-workers indicates that significant challenges remain [72]. With the use of a complete fusion, tandem-affinity-purification (TAP)-tag library for the genome of Saccharomyces cere-visiae, protein expression levels were quantitatively determined with Western blots by chemiluminescent detection. These results were compared to MS-based (MudPIT) results [54,73], and the MS data were strongly biased toward the detection of abundant proteins. For the 75% of the proteome that is represented by proteins present at fewer than 5000 copies per cell, only 8% were... 

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