News from the De­part­ment of Mimivi­rol­ogy

by Elio

Com­bine the new imag­ing tech­niques with the colos­sal and eye­catch­ing Mimivirus, and you'd ex­pect some stun­ning im­ages. A re­cently pub­lished pa­per does not dis­ap­point. The au­thors used sev­eral tech­niques to in­ves­ti­gate how this virus pack­ages its 1.2 mil­lion base pair DNA genome and then dis­charges it into an Acan­thamoeba host dur­ing in­fec­tion. Quot­ing the au­thors:

Trans­mis­sion elec­tron mi­cro­graph of cryo-fixed, sec­tioned, and stained Mimi–virus par­ti­cle re­veal­ing a star-shaped struc­ture. Scale bar: 100 nm. Source

...we show that Mimivirus genome de­liv­ery en­tails a large-scale con­for­ma­tional change of the cap­sid, whereby five icosa­he­dral faces open up. This open­ing, which oc­curs at a unique ver­tex of the cap­sid that we coined the star­gate, al­lows for the for­ma­tion of a mas­sive mem­brane con­duit through which the vi­ral DNA is re­leased. A tran­sient aper­ture cen­tered at an icosa­he­dral face dis­tal to the DNA de­liv­ery site acts as a non-ver­tex DNA pack­ag­ing por­tal.