The Agrawal Lab was the first to determine the cryo-EM structure of an organellar ribosome. By determining the structure of a mammalian (Bos taurus) mitochondrial ribosome (mitoribosome), his group discovered a dramatically altered overall architecture and distribution of its components such as ribosomal RNAs (rRNAs) and ribosomal proteins (r-proteins), as compared to bacterial ribosomes. Their structural analysis allowed them to make several discoveries, including:

  1. In sharp contrast to decades old belief, i.e., since the discovery of mitoribosome in mid 1960s, that the additional and enlarged mito-specific ribosomal proteins (MRPs) in the mammalian mitoribosome physically replace the drastically shortened mito-rRNAs, the Agrawal group discovered that most MRPs instead acquire novel quaternary positions giving the mitoribosome its unique shape that is relevant to mito-specific function.
  2. Two mitoribosomal subunits are held together by greater participation by MRPs, as compared to that in previously determined structures of the bacterial ribosomes. Also, the inter-subunit space, where mito-tRNAs and translational factors interact during protein synthesis, is significantly remodeled and dominated by MRPs, including the presence of a novel MRP feature identified as the P-site finger that was predicted to be involved in regulating movement of mito-tRNAs.
  3. The presence of a unique gate-like MRP feature at the entrance of the mRNA channel in mammalian mitoribosome, possibly required for recruitment of leaderless mitochondrial mRNAs.
  4. That the lower two-thirds of the nascent-polypeptide exit tunnel (NPET) is dramatically remodeled, as compared to that in cytoplasmic ribosomes: NPET in mitoribosome is predominantly lined by MRPs, possibly to help create a unique conduit for the passage of hydrophobic nascent polypeptides and their co-translational insertion into the inner mitochondrial membrane.

Subsequent higher-resolution cryo-EM studies of the mitoribosomes from three different mammalian species, including human, by others and his own group at 2.7 Å resolution confirmed the original discoveries by the Agrawal lab described above, using an advanced cryo-EM technology that became accessible about a decade later with the advent of the direct-electron detecting cameras.

By determining the cryo-EM structure of a chloroplast ribosome (chlororibosome), his lab had revised the decades old assignment of a plastid-specific ribosomal protein 1 (PSRP1) to a chlororibosome-binding hibernation-promoting factor. 

The Agrawal lab continues to study various structural and functional aspects of mammalian mitochondrial translation, including molecular mechanism of steps of translation initiation (mito-IF2, mito-IF3, elongation (mito-EFG1), and mitoribosome recycling (mito-RRF, mito-RRF + mito-EFG2).