Exponential growth in biological sequence data combined with the computationally intensive nature of bioinformatics applications results in a continuously rising demand for processing power. In this paper, we propose a performance model that captures the behavior and performance scalability of HMMER, a bioinformatics application that identifies similarities between protein sequences and a protein family model. With our analytical model, the optimal master-worker ratio for a user scenario can be estimated. The model is evaluated and is found accurate with less than 2% error. We applied our model to a widely used heterogeneous multicore, the Cell BE, using the PPE and SPEs as master and workers respectively. Experimental results show that for the current parallelization strategy, the I/O speed at which the database is read from disk and the inputs pre-processing are the two most limiting factors in the Cell BE case.