Structure of the Monkeypox virus profilin-like protein A42R reveals potential functional differences from cellular profilins

The infectious disease human monkeypox is spreading rapidly in 2022, causing a global health crisis. The genomics of Monkeypox virus (MPXV) have been extensively analyzed and reported, although little is known about the virus-encoded proteome. In particular, there are no reported experimental MPXV protein structures other than computational models. Here, a 1.52 Å resolution X-ray structure of the MPXV protein A42R, the first MPXV-encoded protein with a known structure, is reported. A42R shows structural similarity to profilins, which are cellular proteins that are known to function in the regulation of actin cytoskeletal assembly. However, structural comparison of A42R with known members of the profilin family reveals critical differences that support prior biochemical findings that A42R only weakly binds actin and does not bind poly(L-proline). In addition, the analysis suggests that A42R may make distinct interactions with phosphatidylinositol lipids. Overall, the data suggest that the role of A42R in the replication of orthopoxviruses may not be readily determined by comparison to cellular profilins. Furthermore, these findings support the need for increased efforts to determine high-resolution structures of other MPXV proteins to inform physiological studies of the poxvirus infection cycle and to reveal potential new strategies to combat human monkeypox should this emerging infectious disease with pandemic potential become more common in the future.