Reagents and chemistry firm Promega will enter the protein-array market later this year by debuting a functional array, company officials told ProteoMonitor recently.
As a proteomics player, the Madison, Wis.-based company's presence has been mainly in cell-free reagents and trypsins, and other proteases. But by the end of the year, Promega plans to begin selling arrays based on its HaloTag technology that covalently attaches tags to ligands.
The arrays will be available to customers on demand, Patricia Bresnahan, Promega’s strategic marketing managerfor gene and protein sciences, told ProteoMonitor at last month's Human Proteome Organization's conference in Amsterdam.
“Customers can express their protein with HaloTag in vitro, for example, with our TNT systems and then spot it and covalently catch it on the slide,” she said. “Basically, it's like doing multiple parallel pulldown experiments because now they have a covalently attached protein and that protein can be attached right out of a cell lysate or ... a TNT in vitro reaction.”
Promega’s TNT system is for coupled transcription/translation reactions for eukaryotic cell-free protein expression
“They don't have to go through a purification step to spot their proteins, so this is going to address the need for protein arrays, protein interactions in multiplex, in parallel, and in genomes outside humans, mouse, and rats because it will address any genome,” Bresnahan added.
The company is venturing into this market because of what it sees as a gap in the commercial protein array market, she said. For example, traditional molecular-bearing tools are not addressing the needs of plant researchers, “so people in these model systems don't really have content provided to them in other tools.”
And for those looking specifically for what the firm calls a highly focused subset of data, other commercially available protein arrays, such as Invitrogen's ProtoArrays, may provide too much information.
“We've had a number of people looking, for example, to develop diagnostic tools and as pilot studies to that, to identify antigens, tumor markers, things like that ... they don't need to look at many, many thousands [of proteins],” Bresnahan said.
Promega's arrays are not meant for profiling or discovery purposes. “It's more functional, more for validating, more for experimenting in multiplex fashion for large number of samples,” said Hrissi Samartzidou, global director of gene and protein sciences for the company.
With this launch, Promega will be entering a technology field that has lagged behind mass spectrometry as the technology of choice among many proteomics researchers. Those using protein arrays often have had to resort to making them themselves. Among the small handful of companies that sell them are Invitrogen and Gentel Biosciences.
“We will do it so it will not be cost-prohibitive for the academic researcher.”
The slow adoption of arrays has been mainly due to questions about the quality of commercially available arrays, though Michael Snyder, one of the leading proponents of the technology and a pioneer in their development has said that protein arrays should be viewed as two separate categories: functional arrays and antibody arrays.
While there are issues with antibody arrays stemming from the number and quality of antibodies, functional arrays are much more “mature” field [See PM 11/01/07], said Snyder, who is chair of the department of molecular, cellular, and developmental biology at Yale University.
Slowly, though, there are signs that interest in protein arrays may be growing. Late last year, for instance, a team of researchers at Yale that included Snyder published a study that used a protein microarray method to identify candidate protein biomarkers for ovarian cancer, work they said supports using such a platform for discovery research.
Also, researchers from Harvard University have developed a new protein microarray they claim can enable the large-scale expression of proteins for the first time on such a platform [See PM 05/15/08].
On the commercial side, Invitrogen is seen by many to be the leading protein-array vendor with its ProtoArray products, but Promega officials said its arrays are not meant to compete with ProtoArray.
“We're not competing at all; it's actually a different target” customer that Promega's arrays will be addressing, Bresnahan said. For one thing, ProtoArray products have content and a “very high” density, Bresnahan said. By comparison, Promega's arrays have no content and will have medium density with about 50 microwells per slide, though customers will be able to spot higher density if they wish.
Bresnahan also noted that ProtoArray is meant for auto-antibody screening of disease biomarkers, while Promega's arrays will have the ability to screen antibodies, but will also have applications in enzyme-activity activity assays and for monitoring of protein-protein interactions.
“The unique thing is you don't have to purify these proteins before spotting it, which is a huge effort on the part of other array systems,” Bresnahan said.
The prices for the arrays have not been determined yet but “we will do it so it will not be cost-prohibitive for the academic researcher,” she said.