Plasmodium falciparum displays a large and remarkable variety of heat shock protein 40 family members (PfHsp40s). The majority of the PfHsp40s are poorly characterized, and although the functions of some of them have been suggested, their exact mechanism of action is still elusive and their interacting partners and client proteins are unknown. The P. falciparum heat shock protein 70 family members (PfHsp70s) have been more extensively characterized than the PfHsp40s, with certain members shown to function as molecular chaperones. However, little is known about the PfHsp70-PfHsp40 chaperone partnerships. There is mounting evidence that these chaperones are important not only in protein homoeostasis and cytoprotection, but also in protein trafficking across the parasitophorous vacuole (PV) and into the infected erythrocyte. We propose that certain members of these chaperone families work together to maintain exported proteins in an unfolded state until they reach their final destination. In this review, we critically evaluate what is known and not known about PfHsp40s and PfHsp70s.

We have recently shown that the expression of the DNAJA1 gene encoding a heat shock protein (Hsp40) is a negative marker of meat tenderness in Charolais bulls. To acquire knowledge on the regulation of DNAJA1 expression, we analysed the abundance of DNAJA1 transcripts and protein during development and according to management factors (e.g. feeding treatments, growth path and stress status) in different bovine muscles during postnatal life. We report here a developmental expression profile for DNAJA1 with decreased levels of transcript and protein during the progression of myogenesis. During postnatal life, we found the highest expression of DNAJA1 in the most oxidative muscles. No effect was detected for dietary treatment (pasture v. maize-based diet), growth path (compensatory growth after a restriction period) or pre-slaughter stress status. Therefore, the genetic background and muscle type could be considered as the main factors regarding the level of DNAJA1. Integration of the knowledge gained from this study should help to predict muscle metabolic properties and the ability of the live animals to give high sensory quality meat.