On some Calcaronea (Porifera: Calcarea) from the Barents Sea and adjacent Polar Basin.

Four common calcareous sponge species from the Arctic are described. One species, Sycandra rappi Morozov sp. nov.

A preliminary account of the Arctic/Subarctic Suberites (Porifera: Demospongiae) fauna.

Sponges of the genus Suberites are quite polymorphic and diverse, yet the delimitation of species within the group has always been challenging since there are only a few spicule types that show little, or sometimes no variation in closely allied species. Koltun (1966) created a variety, S. domuncula var.

Biochemical and Structural Diversification of C Photosynthesis in Tribe Zoysieae (Poaceae).

C photosynthesis has evolved independently multiple times in grass lineages with nine anatomical and three biochemical subtypes. Chloridoideae represents one of the separate events and contains species of two biochemical subtypes, NAD-ME and PEP-CK. Assessment of C photosynthesis diversification is limited by species sampling.

TAPBPR employs a ligand-independent docking mechanism to chaperone MR1 molecules.

Chaperones tapasin and transporter associated with antigen processing (TAP)-binding protein related (TAPBPR) associate with the major histocompatibility complex (MHC)-related protein 1 (MR1) to promote trafficking and cell surface expression. However, the binding mechanism and ligand dependency of MR1/chaperone interactions remain incompletely characterized. Here in vitro, biochemical and computational studies reveal that, unlike MHC-I, TAPBPR recognizes MR1 in a ligand-independent manner owing to the absence of major structural changes in the MR1 α helix between empty and ligand-loaded molecules.

TAPBPR promotes antigen loading on MHC-I molecules using a peptide trap.

Chaperones Tapasin and TAP-binding protein related (TAPBPR) perform the important functions of stabilizing nascent MHC-I molecules (chaperoning) and selecting high-affinity peptides in the MHC-I groove (editing). While X-ray and cryo-EM snapshots of MHC-I in complex with TAPBPR and Tapasin, respectively, have provided important insights into the peptide-deficient MHC-I groove structure, the molecular mechanism through which these chaperones influence the selection of specific amino acid sequences remains incompletely characterized. Based on structural and functional data, a loop sequence of variable lengths has been proposed to stabilize empty MHC-I molecules through direct interactions with the floor of the groove.